The Flexible Shaft Machine
This series of 7 articles first appeared in Art Jewelry Magazine. They were a pleasure to research and to write and AJM was a wonderful partner.
Check out my DATES page for It Ain't Just a Drill , my flexible shaft workshops. Please note that all of these articles and the content therein fall under
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#1: The Mysteries of the Flex Shaft Revealed. ©Andy Cooperman 2010
In a dim corner of the college studio where I took my first metals classes hung a dust caked, rusting machine with a kinked --and barely flexible-- shaft and dented handpiece. We drilled tiny holes with this machine and the bravest students occasionally attempted something more, which usually ended badly. Still, I was fascinated by the potential I saw hanging there.
Often misunderstood and underutilized, the flexible shaft machine is actually one of the most versatile tools in the craftsman’s studio. It can speed up and improve fabrication, open new doors into finishing, sanding and polishing; grinds stone, glass, metal, wood and plastic; is wonderful for cleaning up and refining castings and can be used to carve waxes. It can be a hammer and a lathe and its range can be extended by a plethora of handpieces and attachments. In these next six installments I’ll show how the flex shaft is way more than just a glorified drill.
Let’s start with a basic overview. All flexible shaft machines consist of 4 basic components:
·The motor, depending on the model, spins at a maximum speed of 14,000-20,000 rpm (revolutions per minute) with specialized machines
achieving only 5,000 rpm. Motor power nowadays varies between 1/10th and ¼ horsepower, the latter found in flex shaft systems that are
designed for woodworkers or makers who need more torque (rotational force) to carve or move material. Hanging models--the lion’s share-- have integral hangers (wall hooks not provided) and there are models that rest on the bench top itself.
·The rubber or neoprene outer sheath and the steel and brass inner cable (shaft) assembly that transmits the rotational force of the motor
down to the handpiece. This is the flexible shaft part of the machine. The length can vary among brands but is usually about three feet long. The inner cable is easily replaced and is what--if anything--most often breaks on these machines.
·Speed Control. Most often a foot pedal, this controls the speed of the machine which should vary according to the task. There are several
different styles available as well as a bench top dial speed control that a few users prefer.
·The handpiece, which holds a wide assortment of bits and accessories. There are a variety of handpiece styles and configurations available with
many, if not most, being interchangeable.
How high should it hang?
For hanging models, the proper height above the bench is a matter of preference. Ideally, the shaft/sheath should not have to bend too much at the handpiece. With that in mind, many practitioners hang the motor quite high above the bench, maybe ….. inches or …. from the floor (depending on bench height). I prefer my motor quite a bit lower so that I have latitude to change how I position the handpiece relative to the bench pin.
Dremel or Flex Shaft?
Due to its lower cost, many people start with a dremel and then “move up” to a flex shaft. (Dremel is the manufacturer of the Moto-Tool that, like “Kleenex”, has come to mean pretty much any lower priced hand-held rotary tool in which the motor is in the handpiece.) With the noisy, vibrating motor held in the hand, dremel-style tools are a bit clumsy and not really a tool that can execute the more delicate maneuvers that the flex shaft can. Machines with variable speeds (not all are) can reach 35,000 rpm and are usually governed by a dial on the tool itself or on a separate control box. Most often these tools use a collet system (commonly 1/8”) to hold the bits: this can be awkward and limits the range of possible bit shank sizes to only one. Twist drills, which vary in size, are not widely usable.
There are foot pedal speed controls and even flexible shaft attachments (which do not offer the ability to change handpieces) available for these rotary tools but the dremel simply does not provide the precision and versatility that the average flexible shaft machine does. Why settle for a tool that kind of works when the machine that is the professional standard -- one that you’ll more than likely “move up” to eventually --is readily available at a price often under $200 and sometimes even half that?
Which brand? Which model?
So, now that I’ve finished my evangelical bid for the flex shaft it’s time to figure out which is the one for you. As with many tools, the first thing to decide on is the type and amount of use you will be demanding of the machine. The hobbyist jewelry maker or part time craft artist might be able to get away with a lighter duty motor and a more basic flex shaft system. More powerful (higher horsepower) motors are appropriate for machinists, wood workers and carvers— anyone requiring full power and control at lower speeds. The full time bench jeweler, jewelry artist or model maker, will require a good quality, general-use machine that performs well across the entire speed/power spectrum. In the not too distant past there were many manufactures of flexible shaft machines, but the field has narrowed considerably. Here are the leaders:
A name that has become synonymous with the tool itself, it is by far the machine most commonly found in studios and shops and is the template upon which other brands are based. Most specialty handpieces and foot controls are designed to work on this basic blueprint. The industry workhorse for many years was the Foredom’s “S” motor which ran at 1/8 horsepower. The “S” has since been updated to the new “SR” (replacing an older model) with a still more powerful 1/6th hp motor (top speed 18,000 rpm) that can run in forward or reverse with the flip of a switch-- a feature that is more handy than it might seem.
When a drill bit binds and is in danger of breaking, reverse can spell the difference between a bit broken off inside your thick ring shank--usually minutes before the ring is due-- or one that is safely backed out in one piece. And reverse can help eliminate the dreaded “directional matt down” on steel and brass wire brushes, the result of spinning in one direction. For the right-handed, debris can be directed away from the operator’s face when set to spin in reverse and the grab-and-drag-around common to working on the edge of something spinning in one direction can be mitigated by reversing the motor. Any tool that has a non-directional working action--cuts, sands or polishes spinning clockwise or counterclockwise (such as abrasive discs)--can work and even benefit from a change in spin.
But here’s the catch: standard drill bits, burrs and cutters are designed to cut in the forward direction only. They are useless as cutting tools in reverse. (As much as we might like, a reverse spinning drill bit will not deposit metal back in the hole once you’ve drilled too deeply.) And any tool mounted on screw type flex shaft mandrel may have a problem when the right-handed threads of the screw begin to loosen in reverse. (Foredom manufactures reverse thread mandrels, available on their web site.) Still, it’s a nice feature and now stock on what is arguably the new industry standard for flexible shaft machines.
The SR comes standard with a 39” rubber outer sheath and inner cable but also has available specialty sheath/cable combinations of 45” and 66” as well as softer, more limber neoprene sheaths. The basic SR comes with an electronic foot pedal (different than the sewing machine style rheostats of the past) and an adjustable chuck (#30) handpiece.
Sadly, this machine is not available under the "OttoFlex" name. It was made by the Buffalo Dental Manufacturing Co and sold by the Otto Frei Company. Other supply companies once marketed this machine under their own name and machines with the Buffalo Dental label can be found online from dental industry suppliers. This machine features a 1/5th hp motor generating a top speed of 20,000 rpm. The OttoFlex motor housing is a glistening chrome. (Of absolutely no importance but, hey--it’s chrome!) This machine is a dependable soldier and accepts most of the usual foot pedals and handpieces. The one big difference between this and other brands is the stock neoprene sheath, which is very flexible. The advantages of flexibility are obvious but the one drawback to the softer neoprene is that should a bit or tool bind--as it sometimes does-- the more limber sheath/shaft can whap you as the motor spins but the handpiece doesn’t. No real danger, but certainly a surprise! Note that sheaths and shafts are not necessarily interchangeable and replacements should be matched to specific models and manufacturers. Softer, after market, neoprene sheaths available for other brands as well, including Foredom. OttoFlex machines can still be found in the used tool markets of Craig's List, Ebay and yard sales & flea markets.
Grobet and Prodigy
Both of these brands are made in China. The Grobet USA flexible shaft machine is quite economical--often less than $100. The basic kit features a 1/10th hp motor, maximum 18,000 rpm, a standard plastic housed electronic foot pedal and a #30 style handpiece. The Prodigy flex shaft, comparably priced to the Grobet, has a slightly more powerful 1/8th hp motor and the same style foot pedal and handpiece. Rio Grande sells the Prodigy (as do one or two online stores) while the Grobet can be found more widely. As was once the case with things manufactured in Japan, Chinese goods can have a less than savory reputation. That being said, things change and as “made in Japan” now most often signifies quality, Chinese goods are improving. I would still avoid flex shafts from non- jewelry suppliers or very cheap off-brands. But the Grobet and the Prodigy could offer an economical alternative to those who are just entering the field, need a backup or secondary unit or will be using the tool relatively lightly.
Dumore, Pfigst , Pro-Craft and Vigor, along with discontinued Foredoms, once populated a broad landscape of flex shaft makes and models. Why am I telling you about machines that are no longer made or widely available? Because you can still find them on the used or secondary market. Craigslist, Ebay, yard sales and even the newspaper classifieds sometimes have these machines for sale. And while Foredom no longer lists the CC and the S models on their website you can still find these machines new from smaller suppliers if you dig deeply enough online.
The Bottom Line:
Confused? I’ll make it simple.
If you plan on working long and often at the bench or are looking at a career in the metals or allied fields, buy a Foredom SR or an OttoFlex (Buffalo Dental). The 1/6th -1/5th hp that these machines generate will be plenty (a minimum of 1/8th is really needed for certain attachments such as a jump ring cutting jig). They will run you just under $200. Buy only the machine (motor/shaft, handpiece, foot pedal) if the budget is limited but if you can spring for another twenty dollars then purchase one of the basic expanded kits which includes the above along with a nice selection of burs, bits and accessories. They provide a nice survey of what’s available. I would avoid the more extensive kits that simply have too many bells and whistles. If you are a hobbiest on a real tight budget or need another light-duty flex shaft then grab a Grobet or Prodigy motor/shaft, handpiece and foot pedal.
When comparing prices be sure to look at identical or comparable kits or systems. An SR machine may seem really inexpensive at first glance until you realize that the price includes only the motor and the shaft…
Like any tool, the flex shaft ideally functions as an extension of the body. But it is important to remember that the operator is key in this equation. Maximizing the possibilities offered by this amazing tool is a function of control which in itself is a function of practice. It takes time to master this tool. But it is time well spent.
#2: Handpieces & Foot Controls ©Andy Cooperman 2010
As long as the motor is of decent quality and power, the handpiece and foot pedal are the key elements in a flex shaft system. They can spell the difference between a machine that is a joy to use and one that will gather dust --instead of generating it. While matched kits are certainly available, many people customize a system by adding or substituting a specific handpiece or foot control.
The Foot Pedal
There is nothing that will turn a person off to the flex shaft more quickly than a bad speed control. (I vastly prefer a foot pedal to a bench mounted hand-adjusted speed dial and I think that most operators do, although the dial control allows you to set a specific speed.) After a while, your foot on the pedal becomes part of an intuitive feedback loop, responding to what your eye sees, how the motor sounds and the resistance that your hand feels as the spinning tool is applied.
In the dim reaches of flex shaft history, the foot control was a rheostat, like the one on an old sewing machine. More foot pressure, more power to the motor, yielding more speed. Less pressure, less juice, fewer rpm: Simple. But the problem was that at slower speeds the diminished power to the motor resulted in very low torque: bits, burs, drills and polishers were easily bogged down even to the point of stopping. Enter the electronic solid-state foot control which pretty much solves the speed vs. torque conundrum, providing a full range of speeds without loss of rotational force (torque). Most foot pedals today use a “trigger switch” similar to the variable speed switch found on electric drills. While these switches may vary, it is really the materials and geometry of the foot pedal that will set it apart. A really bad foot pedal acts like an on/off switch, resulting in jackrabbit starts that make the motor jump-- and the operator as well. But a good quality foot pedal is smooth and easy to depress. It is sturdy and delivers the full range of speeds from very low rpm to the highest without fatigue. It is a joy. (Can you hear the little Disney birds chirping?) Avoid the old-school little gray rheostats. And if your machine has one, it can most likely be switched out for a good one. (Exceptions: some older and some specialty machines such as the Foredom LX and TX require specific pedals.) So, what are the good ones?
As with most things flex shaft, the basic blue print for most solid-state foot pedals is the Foredom. The company’s FCT is a plastic-housed foot control and the most popular. It works with the CC, S and SR along with the OttoFlex, Grobet, etc. Using identical electronics, the SCT is a heavy metal-housed control, less likely to creep under your bench as you use it. Due to a slightly different hinge system, it is a bit more responsive and is also slightly wider than the FTC. Either of these is a good choice with the SCT sometimes running twice the price of its plastic brother.
·Lucas LowBoy (Lucas Dental)
This narrow, blocky little pedal won’t win any beauty contests but is has proven to be a champ. Talk about geometry… not a curve to be seen on this control, but the way the tread hinges to the pedal makes it smooth and responsive. A precise speed is easily maintained without fatigue or cramping. For years available through the large suppliers, the Lucas went away for a while but has resurfaced and is available on Ebay or directly from Lucas Dental-- at a lower cost than before.. Not sure what, if any, compromises have been made to lower the price but, from all indications, it still seems to still be a great foot control. It is an excellent choice and comparable in price to other pedals. It is also available again from Allcraft. Check the price
As with Lucas, Pepe doesn’t make any flex shaft machines. But they do make a foot pedal that is getting good reviews. Touted for its lower speed control, it is a wide style pedal, quite similar to the SCT and comparable in performance and price.
A Word About Speed:
No matter what speed control you opt for remember that there are a range of speeds at the tip of your foot. Those unfamiliar with the flex shaft often go right for the high end, stomping on the pedal, spinning the motor and hand piece at max rpm, dulling drill bits and losing control of their work. Much of the work with this tool is performed in the mid ranges with polishing and engraving at higher rpm and stone setting and grinding at lower.
Regardless of the make or style (there are many) a good handpiece spins true-- very little wobble--and grips the bit or tool tightly. For general work, there are two varieties: adjustable and quick release. The merits of an adjustable handpiece are obvious. But the cylindrical shape is a bit clunky and changing between flex shaft accessories requires you to locate the ever-elusive chuck key, loosen one bit, replace it and tighten the new one. For someone who uses the flex shaft as their right hand, frequently switching between accessories can be frustrating to the point of exasperation.
The remedy is a quick release handpiece. Most work on a lever system which opens and closes a collet, allowing for chuck-key-free bit change. Many can even be opened as they run. This style is usually more streamlined and hand friendly, ending in a nosepiece which allows for an accurate “pencil grip”. The down side to any collet style handpiece is that it accepts only one size accessory shaft (depending on which collet you use.) Drill bits are the biggest problem here but there are “choked” drill bits that have a standard 3/32” shank terminating in a twist drill. Of course they are more expensive--as are most of the quick release hand pieces that hold them. It is best to leave a burr or bit in place when not in use to keep the collet in adjustment.
The moderately priced adjustable Foredom #30 is both the entry-level handpiece and the industry workhorse. Like the company itself the Foredom #30 is emblematic of the basic, utilitarian flex shaft handpiece.
The 3 jawed chuck accepts the widest variety of flex shaft tools from fine drill bits through the commonly used tool shaft sizes of 3/32” and 1/8” (dremel tools) all the way up through 5/32” whoppers. The #30 style is available with some variations including a one-size collet instead of adjustable chuck but I’d stick to the versatile #30 adjustable version. Most basic flex shaft kits or systems come with the #30 and, if you can have only one handpiece, it would have to be this one. It is easily the most versatile handpiece style available, if not the most streamlined. (There are many non-Foredom models which include “30” somewhere in the name and many of them are just fine but I’d stay with either the original or a “#30-style” from the makers that I’ve listed.)
The Swiss made Techno X was the Cadillac of quick release handpieces. Its rounded, ergonomic profile made it comfortable to use and control. No longer made, it has been replaced by the nearly identical Technique, also Swiss. The only complaint I’ve heard: the once die cast aluminum lever has been replaced in handsome machined steel which can pack a wallop should it snap shut and whap a knuckle.
A really nice, lower end quick release made for Foredom in China. Based on a Swedish model, it grips well, spins true and fits the hand well. Very similar in shape to the Technique but without the whap.
Older style quick release handpieces such as Foredom #’s 18 & 52 and the Faro/Foredom #10 are a bit too slim when compared to the #20 and the Technique, and less fitted to the hand. The #18, especially, has an awkward lever system. Still they have their fans. But for my money, the Foredom #20 is an affordable and dependable choice.
Transforming the rotation of the motor to a hammering action, these little jackhammer handpieces are a wonder for riveting, stone setting and texturing. By delivering the power, the hammer handpiece allows you to concentrate on accuracy. Each concentrated hammer blow is delivered at the end of an interchangeable “point” or steel tip which screws in to the handpiece. Points come in a variety of shapes, including texturing tips-- ultra hard carbide stylus (ideal for stippling and signing work), patterned anvil and diamond tipped “pave” points-- flat or domed points for general hammering and stone setting and blanks designed to be easily modified. The hammering speed--number of strikes per minute-- is controlled by the foot pedal and the strike force is governed by a knurled adjustment wheel. Many brands have come and gone but the two main players are Foredom and Badeco. Points can be switched between brands. REMEMBER: NEVER USE THESE IN REVERSE!!!
Moderately priced at around $100 and well built: overall, a good choice.
Ah, the Swiss: great chocolate and sweet handpieces. The Badeco, more sturdily built and with a more adjustable range of hammer force, is much more expensive, often double the price of its cousin. A great choice for the pro or full time user.
Spring or No Spring:
Regardless of your choice--adjustable, quick release, hammer-- you have the option of adding a “duplex spring” which is designed to act as a flexible joint between the handpiece and shaft, adding maneuverability. Bad choice: these are the first parts to fail-- especially with hammer handpieces-- and have the annoying habit of grabbing hair. Save money, hair and aggravation: Decline the option!
Swapping out Handpieces
I switch between handpieces often. For years they have been designed to pop on and off the end of the shaft. The cable/shaft ends with a fin-like key or tab. This fits into a matching slot inside the handpiece. The beautiful part here is that there is a wide spot in that slot that acts as a funnel or centering device directing the key into the slot at low rpm.
It’s really pretty easy: To remove, grip the shaft with one hand and the handpiece with the other. Lightly step on the pedal and at low rpm pull the two apart. It will pop off. To replace, with the machine spinning at low rpm, introduce the slowly spinning tip of the shaft into the end of the handpiece. Under gentle pressure the key will align itself with the slot. Once they have engaged, the handpiece will spin. As you then firmly push the two together, a small ball bearing in the side of the handpiece snaps into a groove in the metal end of the outer sheath.
#3: Here’s the Drill…. Andy Cooperman ©2011
In the metals studio, drilling a hole is the process that enables many other processes. Piercing and riveting begin with a drill and drills can create pattern and texture. When it comes to the flexible shaft, drilling may seem the simplest of tasks but there’s more to the story. A drill bit is the tool held by a drill (i.e.: the flex shaft handpiece), which is the device that spins the bit, but we often just say “drill”. Drill bits that we use in the studio are made from tungsten vanadium steel or, now more commonly, high-speed tool steel (hss) which is harder and lasts longer. (“High-speed” refers to the steel and not the intended rpm.) There is also carbide, which is very hard, very sharp and very brittle, a “special occasion” bit that can cut harder materials. Diamond drills, steel shanks plated in industrial diamond grit, will cut anything.
·Twist Drill Bits
When we think “drill” it is probably the twist drill that comes to mind; it is the most common. A twist drill is a steel shaft cut with grooves that begin half way up the shaft and end at the tip. The shank is the lower, un-grooved portion of the bit. As with cutting tools such as a file or a graver it can be helpful to think of a drill bit as a chisel. While in this context a file would be a series of small chisels, one in back of the other, the tip of a drill bit has two opposing chisels with cutting edges that face each other and cut as they spin. Like a file the chisel tips cut when pushed into the metal and won’t work when dragged in the other direction so a drill bit won’t cut in reverse. On a twist drill bit these chisel tips are called the lips. The grooves that spiral around the body of the bit are called “flutes”. Flutes don’t really cut; their primary job is to evacuate “swarth”, the cut material (usually chips or windings). Without removal, the swarth will jam up and bind the bit causing it to snap. The base of the drill bit shaft is the shank and usually has no flutes.
. Most have a shank the same diameter as the bit so an adjustable handpiece (#30 style) is required. For those who’ve fallen in love with their quick-release style handpiece, there’s “choked” bits. (At least that’s what I call them.) The various sizes of these little beauties all emerge from a 3/32” shank, the most common size used for flex shaft accessories and for the collets of most quick-release handpieces. The down side is that they cost about twice as much as their straight-shank cousins. And there is also the Adaptor Chuck which holds small bits in an adjustable collet, much like a pin-vice, and has 3/32” shank. Plain or choked, twist drills must usually be ordered in multiples of 5, 6 or 12, although smaller suppliers may offer them singly. Little graduated drill indexes are fine but bits are consumable and I buy certain sizes in bulk.
Speaking of size: I select drill bits by the mm measurement. For ordering, though, I remember the size equivalents of the bits I most often use.
Please note that im my experience, drill bit #'s do not seem to consistently match the mm quoted.
.8mm = 20 ga (approx.) = #61
1mm = 18ga (approx.) = #67
1.6mm = 14ga (approx.) = #52
The tip of a twist drill can vary in steepness (point angle) according to the material it is designed to cut. 118° is an all-purpose point angle common at most benches. I drill through metal, plastic, wood, pearl and even slate with these. (They don’t cut metal well after attacking slate, but they still work on the stone, so I designate them for that task.) Although all-purpose bits will cut plastics, steeper point angles are used in that industry to cut plexiglass and other materials.
Diamond Bits: Twist and Core
For drilling stone, glass, ceramics and hard materials diamond bits are the ticket. Unlike the chisel action of a steel bit, the diamond grit cuts abrasively.
The diamond coating is plated onto two basic shapes: twist and core. The twist bit is essentially a standard twist drill that has been plated with diamond from flutes to lips; the shank is bare. Core drills consist of a diamond coated hollow cylinder, only the rim cuts (like a hole saw), waste material is evacuated through the hollow center and a hole in the side. (There are also solid cylinder diamond bits.) Diamond drill bits come in a variety of sizes and with choked or straight shanks. The Achilles heel of a diamond drill is the bond between diamond and steel. This is where these bits eventually fail due to heat build and is why they are meant to be used wet. I dip the end of the bur in water as I drill or hold work in a shallow water-filled container.
Safety goggles, safety glasses, face shields. Pick one.
Using a sharp drill bit is one of life’s pleasures… Using a dull drill bit is like trying to cut a tomato with a butter knife: tedious, dangerous and in the end a mess. Heat, generated by friction, is the main enemy of a sharp drill bit. It tempers and softens the delicate steel cutting edge. The sound of a flex shaft motor spinning at top speed is the sound of a dulling and dying drill bit. Remember: the foot pedal is not an on/off switch! I start to drill at low rpm and continue at slow speed, gently applying the spinning bit and even pumping the pedal a little. Heat builds quickly in a tiny bit and excessive pressure adds to the friction. Too much pressure can flex and break a bit or deflect it and cause it to wander (like a very fine saw blade) and bits are more likely to bend and snap the further they protrude from the handpiece.
Aside from speed and pressure control the third leg in the sharp-bit tripod, is lubricant.
I have used lip balm in a pinch, but common lubricants include bar soap, wax such as paraffin or bee’s wax, oil (messy), and a variety of waxy cakes with proprietary names like “BurLife”, “ProCut” and “StaySharp”. They come in cylinders that push out like a stick of deodorant or --my favorite-- replaceable cartridges that slot into a simple holder that you screw to your bench. I touch my spinning drill tip to the lube and drill away. My jeweler’s saw blades, burs and anything that needs lubrication gets dragged through the little cone-shaped cake. (I even have one screwed to the bench where I draw wire.) It’s also available in liquid drops. Lubricant is applied to the tip of the bit.
As a bit dulls it is tempting to apply more pressure and speed, which dulls the bit even more leading to more force and more speed until you finally toss the smoking bit away in frustration. Keep in mind what breaks bits:
·Drilling too fast.
·Flex: excessive pressure.
·Deflection: leaning the bit too far off center.
·Protrusion: too much bit sticks out.
·Binding: not clearing swarth.
·A dry, unlubricated bit.
There is almost a sound and feel to a bit just before it breaks. I was taught to pause every now and then and back the bit out to clean debris from the hole. Excellent advice, especially for thick material. Here’s some more: I’ve found that the most dangerous time for a small drill bit is when you’ve almost cut through the metal. Overly cautious, you cut back on the speed and pressure to the point where the thin amount of metal left--foil really- binds and snaps the bit. So continue to drill confidently through that last smidgen just as you did the rest.
A sharp drill bit can sometimes be used without a pilot mark but generally a small punched dimple keeps the bit on target. Pilot marks can also be made with a scribe or even a sharp engraving tool: Dig the point of the tool firmly into the metal just where you want the hole and wriggle the handle around in an arc. This will leave a neat little mark that the drill bit can find and has the advantage of not collapsing the metal as a hammered center punch might. When just beginning a hole, I rest my idle drill in the pilot mark and then gently step on the pedal and begin drilling. But when enlarging an already drilled hole I usually introduce a slowly spinning bit into the hole. This lessens the chance of it caching. Never try to drill are large hole—over 1mm—in one one swipe. To keep a hole centered, where you want it and nice and round, start with a small hole and gradually increase the size of the bit until you are at the diameter you want.
Despite your careful practice this will eventually happen: It’s late, you’re tired and you break a bit off flush in a thick ring. You can’t poke it, drill it or dig it out. But you can dissolve it in a hot solution of alum. Alum can be found at drug stores (it is an astringent) or even at the supermarket in the spice aisle (for pickling). Mix the alum powder with hot or boiling water until no more will dissolve and then toss the afflicted ring in. Use a Pyrex container such as a measuring cup. It may take several hours, but the drill bit will go away. Hot pickle also works. I just throw the piece in and in an hour or so the steel bit is eaten away enough to wiggle it free. Sure, you’ll have a little copper plated area around the hole but that will buff off without a problem. This works with nonferrous (iron free) metals like copper, brass, bronze, silver, gold, platinum, palladium and even aluminum.
A Bit About Mandrels
A mandrel is a tool that supports something else. You can’t drill with a mandrel, but the various mandrels designed for the flex shaft form the foundation for much, much more. There are a boat load of attachments and accessories and the varied shape of each mandrel reflects this. Shank diameters vary between 1/8” and 3/32”. (Can’t say it enough: protect your eyes.)
The workhorse of flex shaft mandrels , and the most versatile, is the screw mandrel. The shaft/shank (3/32” or 1/8”) ends in a female thread and the male screw passes through a hole in the center of an abrasive disc or wheel, a buff--what have you-- - and threads into the shaft, holding everything together. There are many styles of screw mandrels: long screws, shorter screws, heavy shouldered and slim, wide screw heads and small. I like a mandrel with a 3/32” shank which steps up to a heavier shoulder and has a smaller screw head. A wider screw head can provide stability for a soft rubber wheel but can get in the way so I have an assortment of screw mandrel styles. As with most things, find the one that works for you. Screw mandrel are usually sold in packages of six or ten. You can extend the reach of an abrasive disc or grinding wheel by varying the length of the mandrel that sticks out of the handpiece but remember that, like drills, the longer it is the more likely it is to bend or wobble. Most screw mandrels have right hand threads and are used in the forward mode. For those times you want to work an abrasive disc in reverse you can find screw mandrels with a left hand/reverse thread that won’t unscrew as they spin. Oh--the little washer under the screw? It’s there to grip. Top or bottom: doesn’t make a difference.
So many mandrels, so little time. We’ll look at more mandrels as we take a close look at flex shaft accessories.
#4: Being Abrasive: Grinding and Sanding ©2011, Andy Cooperman
If the drill is the tip of the flex shaft ice burg, then accessories are everything below the waterline. I see them as rotary analogs for many processes in my studio: Sandpapers become discs, files are rotarized into burrs and wheels, buffs miniaturized. Shaping, smoothing and finishing follow the standard progression from coarse to fine. (It's worth remembering that you can stop at any point for a variety of finishes.) Flex shaft abrasive and finishing accessories mount on mandrels whose shanks vary in diameter --3/32”, 1/8” and even ¼” -- all accepted by the adjustable # 30 hand piece. Quick release hand pieces will be limited to one shank size, most likely 3/32". The ubiquitous screw mandrel, is the workhorse. A tiny screw is threaded through a hole in the center of a disc or wheel, a buff, etc. and then into the end of this baby. There are different styles of screw mandrels: slim, heavy shouldered, etc. I like a plain mandrel with a 3/32” shank and a 1/16” screw. Most screw mandrels have standard threads, although left -hand threaded are available. They won’t unscrew when, say, using an abrasive wheel in reverse. Oh--the little washer under the screw? It’s there to grip. Top or bottom: doesn’t make a difference. Screw mandrels are usually sold in packages of six or ten. There are also other mandrels, each designed to hold a specific accessory. Animal, vegetable or mineral, if I can hold it on a mandrel, I'll put it in my flex shaft. Which brings me to:
·Split or Slot Mandrels
I love 'em. The shank steps up to a large or medium cylinder or a long tapered cone which is split/slotted down the middle. Rip a little piece of sandpaper--any grit--to about two inches and as deep as the slot is long. Then slide that paper into the slot (I always get this part backwards) with the grit facing you and the paper extending, like a little pennant waving, to the left. Then gently step on your foot pedal and at slow speed hold the spinning sandpaper against your bench pin (or even your finger). It will wrap around the mandrel with the grit outward, becoming a little sanding cylinder. If the paper is on the outside then you have it backwards.
This works great for sanding the inside of rings or for any smaller jobs that require a wide and flat sanding surface, even the outside of a flat band. When the paper gets worn or clogged, just rip off that end and keep sanding. The beautiful thing is that you can change grits quickly without changing mandrels. For a nice satin finish, flatten down one end of a strip of scrubby pad or even steel wool and shove it in the slot. Use slower speeds. Tip: there is a reason that spent sandpaper looks yellow or gray--that’s gold or silver clogging the paper. Save worn out strips in a can until you turn scrap in. Now, let's check out .....
The aggressiveness of an abrasive is governed by grit hardness--what other materials it will cut--and the size of the grit:. 80 is very coarse, 800 very fine. Think about how many grit particles can be packed into one square inch. The finer the grit the more that can fit, so the higher the number. Grit hardness is measured on the Mohs scale (there is no Larry and Curly) which ranges from Talc (1), easily scratched with a fingernail, to diamond (10), the hardest thing we know of.
Why care about abrasive hardness? Unless you want to turn that nice faceted topaz into a cabochon, keep abrasives like aluminum oxide grinders or wet/dry sandpapers away from it! Knowing what a given abrasive will cut--- or scratch-- helps to avert accidents.
-Pummice: 6. Soft and gentle, won't hurt most things. Great for a nice low-sheen finish
-Garnet 7.5: Great for wood and softer materials.
-Emery 7-9: Corundum (aluminum oxide) and other minerals such as magnetite. Great for metal, wood, plastics, etc.
-Aluminum Oxide 9: Pure Corundum (ruby & sapphire). Very hard, cuts very fast. Great abrasive for metal, ceramic, wood, plastic, glass, etc.
Will abrade rubies and sapphires and anything softer.
-Silicon Carbide 9.5: Carborundum. Even harder, sharp and tough. Used in wet/dry sandpapers. Excellent for metal, wood, ceramic, plastic, glass, etc.
-Diamond 10: Cuts anything--including other diamonds.
As abrasive accessories wear down, they get smaller. That material goes somewhere. It’s in the air, on the bench and --if you don’t take precautions--in your eyes, nose, mouth and lungs. Wear a mask and eye protection and check out the catalogs for recommended speeds.
For really moving material--smoothing sprue stumps from castings, trimming a protruding edge or cleaning up a solder spill--the variety in shape and size of grinders presents a versatile arsenal of tools. Most grinders are a cake of solid abrasive, most commonly aluminum oxide or silicon carbide. Abrasive particles cut in any direction (unlike a drill or file ) so they work in both forward and reverse. Use the appropriately threaded screw mandrel.
My Desert Island accessory, these wafer-thin discs mount on a screw mandrel and cut straight grooves. Man, are they useful. Separating Discs come in 3/4, 7/8 and 1" diameters as well as a variety of thicknesses. Available in either reddish brown aluminum oxide (9) or harder, dark gray silicon carbide, either of which will cut anything but diamond. Use the edge or even the side to cut and grind. Standard discs will abrade on either side but there are also "safe sided" discs with one or both sides smoothed and non abrasive. I prefer the standard-- silicon carbide, double sided, 7/8" diameter about .022" (.6mm) thick, leaving a slot (kerf) like a 2/0 blade. Stacking several discs can give a wider slot. Fragile and more spendy, 7/8" X .2mm ultra-thin discs are great when you want a thinner slot, more like a 4/0 blade (cutting jump rings, for instance). Lubrication will prolong their life, just run them into a cake of bur lube. Save smaller, worn discs to use in tight places. Wear eye protection: discs can shatter.
-Making grooves and slots in a variety of materials.
-Clean up the inside angle of a tee seam.
-Cut a groove or lot in the middle of a sheet or tube (plunge cut). Try doing that with a saw.
-Use the side of a standard disc like a flat lap (standard, not safe-sided).
-Cut sprues from castings.
-A variety of surface textures can be made by cross hatching, etc....
·Mizzy & Busch Wheels
The Mizzy is the classic small grinding wheel. Originally designed for dental labs, they don't seem to clog much but wear fairly quickly, an advantage in that there is always a fresh cutting face. They come in a variety of diameters and thicknesses and--you guessed it-- mount on a screw mandrel. These wheels leave a finish like an extra coarse file although it isn't as "sweeping". Gray wheels are slilicon carbide, white, aluminum oxide so they are hard and will grind most things. Mizzys are often used to give a "brushed" linear -line type finish which can be interesting but a bit crude if not applied consistently. Smaller diameter wheels can get into tighter paces, but still can't get into corners. Busch and Mizzy brands are pretty much the same.
Mounted abrasives are shaped masses of abrasive material permanently bonded to a mandrel. There's no screw to get in the way. They are agile and can get into spaces that screw-mandrel wheels simply can’t. Most suppliers offer an abundance of mounted abrasives for the flex shaft in a multitude of grit materials and shapes which include tapered cylinders, cones, inverted cones, tiny wheels, balls, points and bullets. Like a file, you select the profile that best approximates the shape that you are working on. As is often the case with flex shaft abrasives, color-coding varies across manufacturers and suppliers with no consistent indicators for abrasive type or fineness (although aluminum oxide is often reddish brown and silicon carbide frequently black or dark gray). I stick to the medium and fine grit. Mandrel shafts vary in diameter.
Steel discs coated with diamonds. Great for stones, ceramic, glass, metal, etc. Good ones aren’t cheap and best used when another tool won't do.
Sanding and Shaping
While the flex shaft excels at some things, it’s not so great at others. It may not be the best choice for larger areas, where you need a flat and uniform finish or inside some corners where that scrunched up bit of sandpaper works better. But for detail work, complex surfaces and even small flat areas, the flex shaft can do magic.
Pressure Sensitive Adhesive. Basically peel-and-stick circles of aluminum oxide,
silicon carbide or even diamond coated film or paper that you press onto a special mandrel which ends in a 3/4" to 1" rubber disc. Grits vary from 180 - 1200. There is no hole or screw, so the entire area of the disc is available. Spent discs are easily peeled away and discarded. I don’t use these terribly much, because the grit is always “face up” which is not how I usually work, but they can be handy. I find the rubber a bit stiff: it doesn't conform well. Applied in consistent, overlapping arcs, PSA's can give a nice surface.
·Moore's Snap-On Discs
In the center of each disc is a little brass grommet with a square hole that snaps over the corresponding nubbin of a special mandrel (3/32”). Snap on, snap off! Grit coats one side and is most often used facing up. I wasn't crazy about snap-ons until I saw that you can use them grit-side down. It's the side that cuts (not the edge) and I use pressure to bend and flatten the disc so that it lies flat and the sanding surface covers as much metal as possible. They are now my go-to rotary sander. The abrasive on Moore's discs--sand, garnet, emery, aluminum oxide or silicon carbide-- is bonded to either paper or plastic. If you want piles of little brass grommets then use the paper discs -- they don't tolerate flexing or bending. But the plastic does. Diameters range from 1/2" to 7/8". My favorites are the 7/8" plastic backed Adalox (aluminum oxide) coarse (150) and medium (220) discs.
·Drums & Cartridge:
Small sleeves of aluminum oxide or silicon carbide cloth, in a range of dimensions and grits, slide onto a special mandrel with a rubber drum. Tighten the screw in the rubber and it expands, gripping the sleeve. These can be handy for cleaning up the inside of rings, cylinders and bezels--any place that a cylinder will work. Slower speeds are best.
·Sanding Cartridge Rolls.
Not high on my list. A special mandrel supports layers of sandpaper that you peel away as they become worn. I find them to be lumpy and unwieldy and if they get wet, their glue becomes a sticky mess.
· 3-M Bristle Discs
I am slowly becoming a convert to these little abrasive wheels. They are basically “cubitron” grit (an abrasive manufactured by 3M, similar to aluminum oxide) which is embedded in a plastic disc edged in bristles or fingers. For some jobs, they can augment, even replace, sandpaper and are more adept at accessing tight places, like corners or the juncture between prongs. Because these are conforming wheels (the little fingers follow the contour) they excel at evenly removing oxides and scale from complex and detailed surfaces such as reticulation or smoothing concave or undulating forms. Color-coded discs range from 36 to 400 grit. Brown discs, the most aggressive, come in handy for removing the stubborn oxide from forged steel. I use the white and brown discs for a nice matte finish . Used singly, the discs are prone to lose bristles and it’s recommended that they be stacked several deep-- minimum three, maximum six--to present a broader working surface. Apply a light pressure-- it’s the bristle tips that are doing the work. These discs are directional, bristle tips should point against the direction the handpiece spins, so don't use reverse, unless you reverse the discs (and change mandrels).
There are more grinding, and sanding accessories appearing every year but we’ve made a dent. As in every installment in this series, I am speaking from my experience and from my point of view: individual results may vary. This holds especially true for rubberized abrasives, which we’ll look at next time…
#5: Smoothing Things Over: Finishing and Polishing Accessories ©Andy Cooperman 2011
What is gray, green, white, brown, blue, black, has a square edge, a knife edge, is pointy, cylindrical, hard, flexible, is yielding enough to be shaped, can smooth, blend, contour metal, ceramic, plastic and glass, polishes and shines and is available at pretty much any supplier?
Available in an assortment of grits, shapes and sizes, rubberized abrasives are just that: abrasives bound in a solid cake of rubber or plastic. Most wheels are loose and used with a screw mandrel although some come permanently mounted. For some jobs they can stand in for buffing and polishing with bobbing, tripoli or rouge compounds although, as always, large areas are better served by larger buffing and polishing wheels charged with these compounds.
With silicon carbide the most common grit (9.5, see last installment), and a consistent array of sizes and shapes-- wheels, cylinders, and points-- the main differences among rubberized abrasives is the nature of the rubbery binder, how fast it wears and its relative hardness or flexibility. Some say that silicone (not to be confused with silicon carbide) is a softer binder than rubber but that’s not always true. Like a pencil eraser, rubber can have a shelf life, growing dry and brittle over time; silicone doesn’t. Manufacturers include Cratex, Dedeco, AdvantEdge, Pacific, and the dental companies Eve, Edenta and Shofu. Unfortunately, there is no consistent color-coding across brands, one's blue is another's black. Choose these accessories as you would a file: select the one that approximates the shape that you are working on.
Some wheels are listed in inches, some in mm. Generally, my go-to size wheel is 7/8" x 1/8”, approximately 22mm x 3mm.
Some prefer smaller sizes.
Aside from screw and specialty there is the point, spiral or threaded taper mandrel which is like the tapered spindle on your buffing machine. Cylinders, bullets and points, all of which have a hole in the base, are twisted or screwed on. Some people mount wheels as well, but I don't like the protruding end of the spindle.
Fine Tuning: dressing
I consider the factory shapes pre-forms: close but in need of fine-tuning. In the shops where I've worked the bottom inch or so on the flat side of any ring file was invariably concave and shiny, the teeth polished off long ago shaping rubber wheels. (Most of these abrasives are harder than steel or even sapphire and they can damage most stones.) It seems a shame to wound a nice file, so I dress my rubber wheels and points on a large silicon carbide separating disc by spinning it against the disc, which I manipulate to get the shape I need. Square edged wheels can be sharpened into a knife or simply rounded over and points can be made pointier. I often bevel the back edge of a wheel so that it trails off towards the underside. This lets me get in close without hitting the screw. There are also small diamond or carborundum dressing stones.
SAFETY: Wear a mask!!! The abrasive dust is hazardous!
·Cratex: hard synthetic rubber, silicon carbide grit
"Cratex" is often used to mean any rubber wheel. The company has been around for a long time and despite the Cambrian Explosion of brands and species in recent years Cratex is still a popular choice. The rubber is fairly hard and once dressed it holds its edge. I pretty much use only the gray/green extra fine 7/8" x 1/8" thick square edge wheels (which I shape) and points. Cratex seems to come from the factory with a glaze and doesn't perform well without first spinning it against a dressing stone or separating disk to expose a fresh surface. I have found old Cratex wheels to be brittle and of not much use.
-square edge and knife edge wheels, cylinders, bullets (points)
-coarse, medium, fine and extra fine
-mount wheels on screw mandrels, cylinders and points on spiral mandrels.
-will cut most stones including sapphire, steels and precious metals, ceramic,
wood, glass and plastic.
·AdvantEdge : various grits and binders
According to my research and the friendly folks at Rio Grande, this broad family of rubberized abrasives is their baby, available only through them. AdventEdge products come in the usual shapes, either loose or mounted, the latter including small wheels and points similar to Shofu and other dental manufactures (see below). The basic abrasive is silicon carbide but there are also pumice wheels. The big variable within this family is the binder: rubber, silicone or "rubberized", a term that is unclear. In any case, these wheels, discs and points are worth checking out. I primarily use the 22mm x3mm black (medium), silcone, square edge silicon carbide grit wheels for shaping and smoothing, prior to tripoli or matte surfaces. It conforms nicely to round or curved surfaces. The harder rubber version is useful when a crisp edge is required.
·Shofu: silicone rubber, silcon carbide grit.
When I was a sparsely feathered fledgling metalsmith, a young dental technology student named Morty, who was intent on dating my sister, gave me a small kit of crown and bridge polishers (it's still available from some suppliers such as Frei). At that time Shofu abrasives were available pretty much only from dental suppliers, used in the lab-- and the mouth-- to polish metal crowns. I fell in love (so did Morty). Here's the scoop:
-relatively hard silicone binder with silicon carbide grit
-mounted on 3/32" mandrel or loose to fit screw and point mandrels.
- cylinders, bullets, square and knife edge wheels, thin and ultra flexible "floppy" wheels.
-will cut like Cratex but much finer
-coarsest to fine: brownie, greenie, supergreenie.
Brownies are brown, but greenies and supergreenies are actually an identical blue color; the latter distinguished by a little yellow stripe on the mandrel. Shofus aren't cheap so use them to get into places that other things can't, special occasion rather than general clean up. My go-to's are mounted brownie points (bullets) and mounted 5/8" knife-edge wheels (manufacturer # KN7), and less often square edged. The knife-edge is great for cleaning up the corner of a tee seam or even a decorative saw cut for a super thin polished groove (even though the rubber is hard and can hold an edge, they'll need to be dressed or sharpened as you go). Use a light pressure and a medium speed. You can go straight to rouge from a brownie. The greenies and sg's are great for delivering a precise polish in places where you only want a detail to shine like a tiny appliqué-- or a gold inlay on a molar. Try doing that with a rouge wheel. Thanks Morty!
·Skinny polishing rods/pins/points/sticks
Many rubberized abrasives are available in skinny 2-3mm x 1" long rod-like points (no hole). They are held in a special mandrel much like a pin vice or a small drill adaptor. These are wonderful for getting into tight places and can be sharpened into really fine points. The longer the rod extends from the mandrel, the more likely it is to wobble loose or bend under pressure.
·Pumice wheels: great for bezels and prongs
-1/2" to 1" wheels, knife and square edge.
-Brands now include Cratex, AdvantEdge, Dedeco, Silipum. BE CERTAIN THAT THE ABRASIVE IS PUMMICE!!!!
Not very aggressive--- that's the point. Pumice is a 6 on the Moh's scale, so won’t hurt most stones. As a loose powder it provides a nice low luster finish and when bound in silcone or rubber wheels is ideal for cleaning up bezels and prongs in which the stone is set. Cratex makes the classic pumice "Brightboy" wheels in blue or white natural rubber (can dry out), the white being the coarser. There are also Silipum and AdvantEdge wheels-- silicone and pumice-- that remain flexible and hold up well. I like these. The light gray is less aggressive, the green more-- be sure to check with the catalog to be sure. Available in 1/2"-1" square, rounded and knife edged wheels. All can be shaped and dressed. Caution: even though pumice won't hurt most stones heat, generated by excessive speed and pressure, can. Be safe and sane when working around stones. Test the back first if you can.
·Inside Ring Polishing Cylinders.
This shape comes in a variety of brands, grits and rubbers. The cylinders are about 5/8" x 1" with a hole in one end that is threaded onto a strange looking mandrel. Nice tool for the inside of rings or any curved surface. I have had great results "lapping" the outside of a flat band with these.
A precise system of progressive polishers. The coarsest are rubber based. The finer polishers are silcone based and can be used on semi precious stones
hard rubber and silcon carbide. Great for platinum and harder materials like stainless. Too hard and stiff for my taste.
Mounted silicone polishers (most likely silicon carbide), similar to Shofu. Worth a look at.
I really like these silicone wheels because they cut quickly and are a nice blend between hard and flexible. They are similar to AdvantEdge. I use the medium, grey/green wheels (silicon carbide) and the pumice. Search the web for availability.
Finishing: buffs and bristles.
Buffing and polishing with the flex shaft is like using an agile and diminutive buffing machine. Along with variable speed and small size, the great thing is that you can move the work and the buffing wheel, which gives you access to tight spots.
Muslin buffs, hard and soft felt wheels and cones come in a variety of sizes and mount on a screw or threaded point mandrel. Use the same logic as you would at the buffing machine: separate buffing compounds, use wide, soft muslin wheels for broad areas and hard felt for details and high spots.
Brushes: 1/2"-1" wheels and end brushes.
Bristle brushes get a lot of use in my studio, most often for bobbing compound, tripoli and rouge. They are great for accessing small or complex areas. As always, separate compounds. Available in (way too) stiff, medium and soft, natural or synthetic bristles, mounted or unmounted. My brush of choice is the 3/4", medium bristle, mounted. I use them at slower speeds --faster for rouge- charging them frequently. High speeds tend to leave a glaze of baked compound on the metal. I sometimes dip a new wheel in water and then pumice for a soft sheen. Beware the splatter!
Mounted Wire Brushes: 3/4"-1" wheels and end brushes.
Permanently mounted steel or brass bristles that burnish as they spin.
Wonderful in any situation that would benefit from a satiny finish; especially awesome for bringing a reticulated surface to life. Although conventional practice calls for using brass on yellow metals and steel on silvery, I use a 3/4" medium soft steel wheel at slow speeds for everything. Dipping the brush or the work in a jar lid of soapy water can improve the finish a bit but it is messy-- never put a spinning wheel in the water! Wheels with crimped wires are stiffest. Occasionally using them in reverse keeps them from matting in one direction.
There is a variety of scrubby-type wheels that produce a satin finish. Brown, green, white indicates aggressiveness (check the catalog). I often make my own by cutting a little disc from a kitchen pad and then poking a hole in the center. They don't have to be perfect. (Sounds like heresy, but I stamp out mine out with my disc punches.) Use a screw mandrel.
This section has been the most difficult to write due to the overwhelming and ever increasing diversity of brands and types. The bottom line on all these accessories is experimentation. Order a selection and get scientific. Mark each one --you can write the serial # and supplier on the side of rubber wheels with a fine point permanent marker--take an afternoon and try each, Then record your conclusions: "Too stiff, too fine, falls apart, glazes, etc". You'll know in a minute which works best for you. Next time we'll sink our teeth into burs.
#6: The Old Grind ©Andy Cooperman 2012
What can you do with burs? Grind, carve, excavate, enlarge, trim, fit, adjust, mill, stone set, create surface and texture, make catches and fill teeth. (You didn’t think Dr. Fillgood is actually using drills, did you?) Steel burs can cut metal, wax, wood, plastics and composites. The easier question might be: What can’t you do with burs? I often reach for a bur before I grab a file. But I’m getting ahead of myself. Let’s start at the beginning. Is it “bur” or “burr”? I’ve seen it spelled both ways but the most common is “bur”. (Ironically, burs are sometimes used to remove “burrs”, the ragged bit left after drilling). I think of it burs this way: Wrap a file around a shaft or shank and you have a spinning file-a rotary file-- a bur. Burs cut in the same way that files do. And like a file, getting the contour that you want in your work first depends on the shape of bur that you choose. The most common shank diameter for burs is--you guessed it-- 3/32” (2.3mm). They are available as singles, in sets of graduated sizes or different shapes or in same-sized six packs. A sharp bur is one of life’s pleasures. Like drills, lubrication can make a dull bur seem sharp again. Use the same lube that you would for drills. Remember, most burs won’t cut in reverse.
Burs are available in tungsten vanadium steel (tungsten), high-speed tool steel (hss), diamond and carbide. Carbide is very hard and brittle and least commonly used. Tungsten and hss are widely available and form the backbone of catalogue burs. hss is harder and more heat resistant and generally will hold up longer but there is a broader profile (shape) selection of Tungsten burs. (There are also “blackhead” tungsten burs which are specially hardened and tempered and those coated in yellow colored titanium nitride, both designed to prolong life.) Because they are machine cut, tungsten burs are consistent in diameter and tooth angle. Hss burs are all cut by hand (wow!) by tiny little men using diamond grinding wheels and jigs, so they vary a bit (only kidding about the little folk). The teeth are usually cut in arcs radiating from the center as opposed to the straighter ones on their tungsten cousins. Generally, tungsten vanadium burs are about one third the cost of hss. Tungsten are commonly available in 6 packs. HSS burs can be re-sharpened, although they will come back a bit smaller.
HSS (High Speed Steel): Spearhead, Elite.
Tungsten Vanadium: Busch, Braessler, Fox, Dentsply Maillefer, Lynx.
Brands carried by vendors will vary but an extensive selection of styles can be found in pretty much every catalogue. Prices for the same style and size of bur can vary widely among manufacturers.
The cut (tooth size) of burs is not as extensive as in files: there’s pretty much fine and standard. But like files, burs come in Single Cut or Cross Cut. The latter cuts much faster and the second set of cuts is said to help chip out the swarth, leaving a cleaner cut. Not all shapes are available in cross cut. Hss burs aren’t fully cross-cut but they do have several cross-cut lines in them to help evacuate material.
As I’ve said, shape or profile is key,. I use one shape of bur for a multitude of tasks by using different parts: the side, the tip, or the edge, etc. And I may use several shapes, one after another, to get the result that I want. Here’s a few profiles that I use, plucked from the multitude.
·Round or Ball
I consider the ball the “cockroach of burs” (I’m getting tired of writing “workhorse”). For me it is the ultimate generalist. I use ball burs from 15mm on down to .4mm for a wide variety of tasks. The sizes that I use most often I buy in 6 packs, usually tungsten vanadium, although I have several graduated sets of hss ball burs. At my bench, a big ball burr is essential for trimming edges or grinding contour. I use the equator for that. The tiniest ball burs work great for signing and hallmarking work. It isn’t easy but once you get the hang of it… I rarely use the very tip/top of a ball bur using instead the top/side of the ball. Normally the shank is at somewhere around 45˚ to the work. Use them for any sort of countersinking application, for grinding round-bottomed seats for pearls and for texturing. Grind fairly deep over lapping divots for a peened effect. Tungsten ball burs range to 5mm.
·Bud or Flame
If you held my feet to the fire, I’d have to say that, technically, flame burs are longer and more gently tapered than buds. But they are pretty much the same shape. A cousin to the ball, the bud bur is great for counter sinking (use the tip), relieving and general grinding (sides). It is really handy for stone setting too. Some jewelers use it to grind tapered seats for flush sets. I have used its elongated, rounded side for prong or tube/bezel setting deep bellied “native cut” facetted stones. After defining the seat with a setting bur, I follow with the bud which grinds away material for the bulbous pavilion.
·Cylinder: Tapered, Square.
Next to the ball, I use a variety of cylinder burs most. Tapered cylinders, square (straight), cross cut and single cut. Tungsten vanadium range in size from maybe .6mm to about 3mm while hss range up to 11mm whoppers. I use cylinders whenever I want a groove, to extend or widen a drill hole, to carve clasps or to trim straight walled areas like bezels. If I were soldering a wire at right angle to the edge of a sheet, I might grind a little depression in the sheet edge with the appropriately sized cylinder bur to form a seat for the wire to sit in. I mostly use the sides of the bur. Both the sides and tip of the cylinder have teeth.
The long taper of the krause is kind of like a cross between a cylinder bur and a flame. The attenuated tip sees most of the work, it is perfect for cleaning up filagree or getting into the corner of square hole or bezel or the chevron of a marquis setting; anyplace that requires an agile little grinding point. Cylinder and krause burs have an Achille’s Neck. The point where the cutting head meets the shank can be narrow and delicate and since these burs are often used with lateral/side pressure, they can snap off. Consider it a refining bur.
·Hart/ Baring Cutter
They look like the pavilions of two facetted stones glued girdle to girdle or maybe a flying saucer with a very sharp equator, or a squat baseball diamond. In any case, they are used in stonesetting: prong, multiple shared prong, flush, channel, even bead and bright cut. The edge (sharp equator) is used. This bur is really about manipulation. Apply the spinning bur to a sheet of metal and you have a notch. Drag that spinning bur and the notch elongates into a channel. Move it along a curved line in a piece of sheet and that channel becomes a carved score that will allow the metal to fold along that curve with a crisp edge. I use it a lot for texturing, especially flat bands or the rim of a brooch: if you drag the bur a bit in parallel lines it yields a pattern like a very sharp forging hammer. It can also make cross hatched lines akin to Florentine. I’m not sure what distinguishes a hart bur from a baring cutter (a baring is like a channel or a stone seat), but a hart is often described as 90˚ or 70˚. This shape of bur is also available in 45˚ which I suppose makes it the “baring cutter” by default.
In profile these burs echo the pavilion of facetted stones. Like a pavilion, the front half of the setting bur comes to a point. Where the girdle and then the crown would be on the stone, the setting bur continues up to a flat/vertical side. Many setters prefer tungsten vanadium setting burs: they are uniform, fairly tough and less expensive. Setting burs are used in all type s of faceted stone setting. Some jewelers and setters manipulate a small sized bur grinding a seat into each prong (some even use hart burs this way) or slowly grind a seat into the wall of a heavy bezel, believing that this offers the best control. (These bezels would be thick sterling, gold, platinum, etc. rather than a thin fine silver bezel strip.) For round stones, other setters use a setting bur just a hair smaller than the diameter of the stone and grind the entire bezel or all the prongs at once. A smaller bur compensates for the slight eccentric wobble that all handpieces have which has the effect of grinding a larger seat.
Even though I set stones less these days I use setting burs all the time. The sloped and pointed portion makes beautiful countersinks--great for relieving and refining a hole on the inside of a ring, azure style. The vertical/straight sides can be quite generous in width and I use these to grind sides and edges or an inside seam of a ring where it was sized or soldered.
·Cup or Concave Cutter
Prepare to wince: My cup runneth over with uses for this bur. Well, maybe not runneth over, but it is a handy little animal. It is basically a cup with teeth inside. Kind of Freudian, I guess. I believe that these burs were designed for rounding and finishing the tips on prongs (although a round prong tip is not always preferable). They cut and burnish. You can use them for rounding and refining the tip of any wire, especially posts and ear wires. They are really useful for finishing the head of a rivet. I try to gently manipulate the handpiece in a circular fashion to help the cup create a dome. The art with these burs is in selecting the proper size. Too small and it gouges and scores the rivet, prong or post; too big and it can clip the stone or leave a ring around the rivet. The cup should just about cover whatever you are grinding.
Cup burs range from .9mm all the way to 10mm (which is a pretty hefty prong tip).
These big boys can be carefully used to refine round bezels or to finish the end of a rod or really big rivet. There are now several species of cup bur. Busch makes a squashed looking cup, designed to get into tight places; there are also cup burs with slits in the sides that keep them from clogging. I’ve heard that these slit cups give a nice round tip with a great finish.
Straight sided cones and reamers are good burs for countersinking, gently widening a hole. Generally they have a more acute taper than a tapered cylinder bur and a sharp point.
A special-occasion bur, the inverted cone can really save the day. Let’s say that
for some reason there’s a blob of solder inside a tube or bezel where it meets the back plate or too much solder has flooded that inside corner (of course, I am imagining this since it has never happened to me). You can’t get in there with a file or a disc. You could use a round bur but that wouldn’t get in the corner and in any case would gouge the bottom rather than leave it flat. You could get in with a cylinder bur and use its flat tip and side to grind…. But chances are you’ll end up grinding right into the side wall. What you need is a bur whose cutter is wider at its tip than where it meets the shank--a reverse taper or a flare. The inverted cone has teeth on its sloped sides and its flat, wider tip. Holding the shaft at 90˚ to the base sheet so that the tip of the bur rests flatly, use the bur like a router, moving it in small circles and arcs. The flat bottom will cut the solder glob, while the edge of the bur nibbles its way into the corner. Go slowly. Because the taper is inverted, the side of the bur slopes away from the bezel/ tube wall. The bottom gets cut (machined) and the corner is left nice and crisp while the wall is left alone…. It takes practice.
Their squared edge makes them great for grinding flat areas between uprights or carving and refining the bottom of a trough as in preparing a channel setting.
Used in lapidary, jewelry and dentistry, diamond burs are the ticket for working with stone, ceramic, glass or hard metals, anywhere an abrasive type of cutting is preferred. They come in a variety of shapes and quality. I always have a few diamond ball, bud and cylinder burs on hand.
There are special bur sets designed specifically for wax carving and there are also strange little three-bladed propeller burs called wax paddles. These improbable burs cut file wax quickly and cleanly without clogging. There are florentine burs, large cylinders that cut parallel lines: cut in one direction and then come back and cut across those lines. Oval, knife edged, round edged wheel burs are a few more and there are more still.
When I started out, my first burs came from the family dentist. (It was the least he could do.) They were smaller versions of our jewelry burs and, while they were used (and autoclaved), they were still pretty sharp. The problem was that they only went up to 2mm or so. But I still use them today and dental lab catalogues are a good place to find strange burs.
Burs can take a while to master. They pull your hand away from you as they spin and can do damage really fast. You can’t just hold a bur--or any tool--up to the work and step on the foot pedal; it’s important to remember that success in using burs lies largely in skillful manipulation.
Here’s a few things to remember:
-Burs, especially tungsten, are consumable.
-Wear eye protection and watch your fingers.
-Dropping a handpiece is a great way to break a bur.
-Nibble rather than gobble (pressure and speed wise, eating too).
-Use sane speed.
I’ll close by saying “thanks” to John Frei for his patience and ready willingness to share his encyclopedic knowledge of tools, in this case burs, drills and flex shafts. (I think he really enjoys it.) Stay tuned for our final installment.
#7: Loose Ends and Tricky Business ©Andy Cooperman 2012
Well, we’ve reached the end of this series. This seems like a good place to attend to things that didn’t fall neatly into previous installments and to trot out a few tricks: nifty things they don’t teach you in school-- or in books.
Here’s a few doodads that make your shaft more, er, flexible. (Sorry.) These rely on the #30 or similar style hand piece. Prices are approximate.
Foredom makes two models: the DP30 and the DP39. Both have stops to allow for preset hole depths; the more expensive DP39 sports a depth indicator dial. $169/239. Foredom units are nice and rigidly built. Hand pieces and shafts not included.
2” Angle Grinder
When I began to work on larger projects -- home remodel, sculpture-- I quickly came to depend on a five-inch angle grinder, the tool that welders and body shops use. After years working with the flex shaft that tool just made sense. Wouldn’t it be great if someone made a smaller version for the shaft, with the grinding disc offset ninety degrees to the handpiece? Well, Foredom does. Use your own #30 or get the kit complete with a handpiece and a selection of abrasive discs and wheels. Great for stone carving, wood work and all sorts of projects. $119/$169. NEVER USE IN REVERSE
Translating the advantages of a belt sander to jewelry scale- with the added benefit of variable speed-- there are two makes of flex shaft belt sanders. Belts can be switched and replaced on each. The Foredom requires a #30 style handpiece and uses a 9/32” (about 7mm) wide belt. The standard model comes without a handpiece; a kit version includes one along with an assortment of belts. $71/$132. Since the Foredom connects with the handpiece rather than straight to the shaft it will work on either US or European (slip-joint) style shafts.
The Kate Wolf sander is a complete unit-- it is the handpiece--you simply snap it on or off the flex shaft as you would any handpiece. Designed to work only on US style key tip flex shafts. At $179 it is the spendier of the two but features a wider, 1” belt. The Wolf also comes with a bench clamp (adjustable to any angle) and belts and is available with the GRS (benchmate) mounting cleat-- very nice!.
Matt Wax Trimmer
A good tool if you are carving waxes, this trimmer consists of a flat, adjustable angle platform that clamps to the # 30 (not included). A burr (a large cylinder for trimming ring blanks, for instance) is held in the handpiece chuck and the wax can then be rested on the stable platform and slid up to the spinning bur to provide a consistent cut. Think router table. A variety of bur shapes can be used. I imagine that other materials such as wood and plastic can be used.
It's tempting to start adding all sorts of handpiece attachments to your flex shaft arsenal, after all, you only need one #30. But in practice disassociating the handpiece from each attachment and reassigning it can be a pain, especially In the heat of the metalsmithing moment. It would be ideal to have a flex shaft machine consigned to each attachment but who can lay out the cash? (Dedicating a machine to the stationary drill press is a good solution, though.) A decent compromise for the mobile attachments -angle grinder, wax trimmer, etc-- is to dedicate a #30 to each: the assembly can then simply be switched out like you would any handpiece. I know: to the light user this sounds excessive. But I am looking at things through the eyes of a professional where time can mean money. Here’s some more gadgets.
Mounting Clamp for Bench
Takes the hand out of the handpiece, immobilizing it so that it can be used as a stationary workstation. There are several handpiece clamps out there, usually 2 blocks of plastic that close around and grip the cylindrical body of a #30 style handpiece. Some have hardware that clamps to the bench while other clamps are themselves clamped between the jaws of a bench vice.
Like a hammer handpiece in its action, the MagnaGraver accepts gravers (that have been altered to fit) and holds them with a setscrew mechanism. The more versatile 11VP ($225/325) accepts all sorts of tools from gravers to wood chisels (change collets) and also has an impact adjuster to govern the force of each blow. Not sure what to say about this tool. I’ve used it only once and the experience didn’t stick with me….
Shared Flex Shaft Foot Control Panel (Multiple Shaft Switch)
Awesome. Up to five flex shaft machines can be used (one at a time) all controlled by the same pedal. Pull one handpiece/shaft from its slot in the switch panel and that one goes “live”. No more searching blindly with your foot for the right pedal. If you have more than one shaft and are using multiple foot controls this gizmo is calling your name. One more nice thing is that any motor that can be used with a foot pedal will work with this switch. Otto Frei is the only supplier that I can find who now carries it.
It doesn’t seem right not to mention the tool what could be seen as the evolutionary legacy to the flexible shaft. With the motor contained in the handpiece and no shaft to weigh you down, the micromotor is similar to a Dremel. But the similarities really stop there. Different makes and models will vary but, in general, the handpiece is light, agile and well balanced, it runs smoother, truer and much faster and the power supply/control unit can run several handpieces. Most micromotors offer reverse, dial speed or foot pedal control, adjustable chuck and quick-release handpieces; some offer hammer and specialty handpieces --even belt sanding attachments. Performance varies widely, so do your research. Now, here’s a few tricks:
Cotton swabs, toothpicks and bamboo skewers: neat little finishing aids for tight places. I use the cardboard or wood shafted swabs-- the hollow plastic ones will collapse. Snip the swab mid-shaft and chuck the stump. The cotton end can be charged with tripoli, rouge, etc. and used as a tiny buff or it can be snipped off entirely, the cardboard/wood shaft spun/shaped against a separating disc, charged and then used like a hard felt buff. Similarly, toothpicks (the round wood ones) and kabob skewers can be cut to size, shaped and used as micro finishers.
Miniscule but Mighty
The smallest members of the versatile ball burr family can be the handiest.
·Use a 1mm or smaller bur to grind a "kernel" -pilot mark- prior to drilling through a tube or into a hollow object. Try doing that with a center punch!
·Sign your work with a .4mm ball bur. It takes practice, patience a steady hand but gets you into places that a stamp won't go. You'll have to vary the moor speed as you make your way around each letter.
·Use a .4mm or so bur to replicate a texture, such as reticulation, that has been compromised by an accidental solder spill or finishing slip.
Pull it True
I always plan for the worst. If I need to drill a 2mm hole dead center in a rectangular sheet, I'll always start small, below 1mm, to allow for mid-course correction. A small hole drilled awry can be "pulled" to center with a narrow cylinder or Krause bur. I thread the bur into the hole and grind at the side, enlarging the hole until it is more or less centered and then use a larger drill bit to clean up the slightly irregular hole. I finish with a 2mm bit.
Make it Safe
A file with a "safe", non-cutting side can be really handy and there are times when a bur with a safe side can save the day. The side of a cylinder or inverted cone bur can be ground smooth by slowly spinning the teeth against a separating disc until they are gone. Since only the teeth on the end remain, this "improved" bur can be used to refine the bottom of a hole, a channel or bezel without harming the side walls. Try "safing" the bottom of the bur or other bur shapes as well. But remember: there's no going back.
I have my shaft hanging fairly low so that I can hold the handpiece, chuck facing up, steady against my bench pin without over-bending the shaft. In this way, I can bring work to the spinning chuck using, for instance, the side of a separating disc as an abrasive turntable or lap against which I can sharpen tools or file a point on a piece of wire by spinning it in my fingers against the disc. The possibilities are endless.....
Something's Gotta Spin...
...but it doesn't necessarily have to be the tool or bit. Try spinning the work instead.
Tube and Rod.
Filing a perfect, true end on a tube or rod isn't rocket science, sure, but it can also be done quickly and accurately if the rod/ tube can be fit in a #30 style handpiece. It needs to be less than 5mm in diameter (to fit in the chuck)and not attached to anything. Chuck a short length-- under two inches, too long and it will wobble-- and hold the handpiece as just described. Step on the pedal so that the shaft spins -- in forward direction-- at a relatively slow speed. Now here's the tricky part: hold a flat file flat on the face of the tube nearest you with the teeth of the file facing into the spin. Holding the file in your right hand, the teeth will be pointing to the left, into the direction of the spin. You'll feel the teeth bite and see metal filings. Because the tube is spinning into the file teeth, the whole face of the tube will be planed. No harm will be done if the file is held on the opposite see of the tube: it just won't cut. Like many flex shaft techniques, this takes practice.
Believe it or not, sometimes it pays to make your own ear posts. The big problem is how to get that little safety groove near the end of the post. Using the same technique above, chuck the proper length of post wire ( I use 20 ga) into the #30. As it spins, pinch the wire about 2 mm from the free end with a pair of slender round nosed pliers -use firm but not Insane pressure. I lube the plier jaws with some wax or bur lube. As the wire spins, the pinching pliers will swage or compress a necked-in groove into the wire without removing any material and weakening it. Now, file that end of the post true (spin it!) and then hold the appropriately sized cup bur against it, moving your wrist in a little circle. This will cut a nice dome on the post end. Finally, flip it around and file the solder side flat.
Leave Your Mark
Selecting the proper size of cup bur to finish a rivet head can be tricky: too large a bur can leave a ring 'round the rivet. But if done evenly, this can leave a smart, machined effect.
Ah, the old separating disc...great for so many things, like cutting slots, or grooves. They can be stacked on a screw mandrel for a wider cut and, for cutting multiple, parallel grooves, slots or tabs, try stacking two discs with a small spacer in between. Just drill a hole the same diameter as the mandrel screw in a small disc or piece of sheet (doesn't have to be round even, just small in width, maybe 3mm or so). The thicker the spacer, the further apart the slots or wider the tab. And don't forget that ultra thin .006" separating discs are a great way to cut jump rings. No "accordion action" and a neat, narrow kerf.
Got a little casting porosity or a pit in a solder seam? Take a trip to the hardware store and buy a small steel "eye screw" (machine thread not wood), maybe 1/2" diameter. Take a minute and polish the zinc plating off the end, leaving the steel shiny; don't worry about the threads. Chuck the threaded end into the handpiece and, spinning at low speed, firmly hold the spinning loop end of the eye screw against the offending porosity, moving back and forth across it. As it spins, the two sides of the "eye" loop act as hammers, pounding the metal and closing the pits. You will still have to finish the metal. I have also used this to upset (edge forge) or thicken the rim of a raised cup --or any edge, for that matter. The hole in the middle of the "eye" becomes transparent as it spins so you can see the work. Sweet!
One of the first things I learned in my first post-school bench job was how to put a hammer finish on a wide band. Now, I thought I already knew how to do this, so I cockily stepped forward to take the job on, threaded the band onto a ring mandrel and, wielding my domed hammer, put a nice, deep plannished finish on the band. My seasoned coworkers looked on, jaws agape as I pulled the band from the mandrel: I could fit my leg through it. Mercifully and without further humiliation they showed me how it's done: You grind the hammer marks one by one into the properly sized band with a hard rubber abrasive wheel like a Cratex brand extra- fine, with the edge sculpted into a dome shape by spinning it against something abrasive like a separating disc. Maneuver the wheel a little and dig into the metal until the mark is how you want it. It looks more like a hammer-finished band than a band finished with an actual hammer and the band isn't stretched. Wear a mask.
Well, there you have it. It's been fun and --I hope--informative. I’ve certainly learned a bunch. There is so much that the flexible shaft machine can do but, like any tool, it can take a while to master and, in the end, it depends on the skill of the hands using it. It 's been my job (and pleasure) to open some windows into what this tool can do. Now it's up to you to open some more. Be careful, be safe and try to think outside of the box. Thanks to John at Frei, Mike at Foredom, Tevel at Allcraft and the folks at Rio Grande. And remember: the flex shaft is WAY more than just a drill.