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How to use a flex shaft

Part 1 of 7: Flex shaft fundamentals
Flex shaft diagram

1. The motor, depending on the model, spins at a maximum speed of 14,000–20,000 revolutions per minute (rpm). Some specialized machines reach only 5,000 rpm. Motor power varies between 1⁄10 and 1⁄4 horsepower (hp); the latter is found in flex shaft systems designed for woodworkers or makers who need more torque (rotational force) to carve or move material. Most models have integral hangers (hooks not provided); some models rest on the bench top. 



2. The rubber or neoprene outer sheath and the steel-and-brass inner cable (shaft) assembly transmits the rotational force of the motor to the handpiece. This is the “flexible shaft” that gives the machine its name, and it’s usually about 3 ft. (91.4 cm) long. The inner cable is what (if anything) most often breaks, but it is easily replaced.



3. The handpiece holds a wide assortment of bits and accessories. Handpieces come in a variety of styles and configurations; many, if not most, are interchangeable. The #30 handpiece is the most common and the default for most flex shaft models. These handpieces have an adjustable chuck that is loosened and tightened with a chuck key.


4. The user employs a speed control — most often a foot pedal — to alter the machine’s speed to suit his or her task. There are several styles available as well as a bench-top dial speed control.

Each Sunday for the next 7 weeks, we will be posting a different part of our series "How to use a flex shaft"

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 used it to drill tiny holes. Occasional attempts by the bravest students to do something more usually ended badly. Still, I was fascinated by the potential I saw there.

Often misunderstood and underutilized, the flexible shaft machine is one of the most versatile tools in the craftsman’s studio. It can speed and improve fabrication; open new doors into finishing, sanding, and polishing; grind stone, glass, metal, wood, and plastic; clean up and refine castings; carve waxes; and act as a hammer and a lathe. A plethora of handpieces and attach-ments extend its range even further. In this series of articles, I’ll show how the flex shaft is much more than a glorified drill.

Dremel or flex shaft?

Like “Kleenex,” “Dremel” is often used as a generic term. Dremel rotary tools are manufactured by Robert Bosch Tool Corporation, but we tend to associate “Dremel” with any lower-priced handheld rotary tool that houses the motor in the handpiece. 

Due to its lower cost, many people start with a Dremel. But because the vibrating motor is held in one’s hand, Dremel-style tools can’t really execute the more delicate maneuvers that flex shafts can. Dremel-style machines with variable speeds can reach 35,000 rpm and are usually controlled by a dial, either on the tool itself or on a separate control box. Most often these tools use a collet system (commonly 1⁄8 in./3 mm) to hold bits, which limits the range of bit shank sizes to just one.

There are foot pedal speed controls and even flexible shaft attachments, which don’t offer the ability to change handpieces, for these rotary tools, but they simply do not provide the precision and versatility that the average flex shaft machine does. 

Which brand? Which model?

As with many tools, the first thing to decide is what kind of work — and how much of it — you’ll demand of the machine. For a hobbyist jewelry maker or part-time craft artist, a lighter duty motor and a more basic flex shaft system would be sufficient. 

Anyone who requires full power and control at lower speeds — machinists, woodworkers, and carvers — would need more powerful motors, with higher hp. 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 manufacturers of flex shaft machines, but the field has narrowed considerably. Here are the leaders:


A brand name that’s become synonymous with the tool itself, Foredom is by far the machine most commonly found in studios and shops; it’s the template other brands are based upon. Most specialty handpieces and foot controls are designed to work on this basic blueprint. 

For years, the workhorse was Foredom’s “S” motor, which ran at 1⁄8 hp. The “S” has since been updated to the “SR,” with a more powerful 1⁄6 hp motor (top speed 18,000 rpm) that can run in forward or reverse with the flip of a switch. This feature is more handy than it might seem.

When a drill bit binds, reverse can mean the difference between a bit that breaks off inside your thick-shank ring and one that gets backed out in one piece. Reverse can also help eliminate the dreaded directional matt-down on steel and brass wire brushes, the result of spinning in one direction. 

A right-handed user can direct debris away from his or her face by setting the tool to spin in reverse, and the tool’s tendency to grab and drag a piece when one’s working on the edge of it can be mitigated by reversing the motor. 

Any tool that has a nondirectional working action — that’s a tool that cuts, sands, or polishes whether spinning clockwise or counterclockwise (such as abrasive disks) — can work and even benefit from a change in spin.

But here’s the catch: Standard drill bits, burs, 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 tool won’t deposit metal back in the hole once you’ve drilled too deeply.) 

And any tool mounted on a screw-type flex shaft mandrel may have a problem when the right-handed threads of the screw begin to loosen in reverse. (Foredom does manufacture reverse-thread mandrels, which are available on their website.) Still, reverse is a nice feature, and it’s now stock on what is arguably the new industry standard for flex shaft machines.

The SR comes standard with a 39-in. (1 m) rubber outer sheath and inner cable; specialty sheath/cable combinations of 45 in. (1.1 m) and 66 in. (1.7 m), as well as softer, more limber neoprene sheaths, are also available. The basic SR comes with an electronic foot pedal (different than past sewing-machine-style rheostats) and an adjustable-chuck (#30) handpiece.


This machine is made by the Buffalo Dental Manufacturing Co. and sold by Otto Frei. Other supply companies once marketed this machine under their own names, and you can find machines with the Buffalo Dental label from dental-industry suppliers, but Otto Frei remains the best buy. 

This machine features a 1⁄5-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 big difference between this and other brands is the neoprene sheath, which is softer and very flexible. The advantages of flexibility are obvious; the one drawback to the neoprene sheath is that, if a bit or tool binds, the more limber sheath/shaft can whap you as the motor spins but the handpiece doesn’t. No real danger, but certainly a surprise! 

Softer, aftermarket neoprene sheaths are available for other brands as well, but sheaths and shafts are not necessarily interchangeable. If you need replacement parts, make sure they match the specific model and manufacturer of your machine.

Grobet and Prodigy

Both Grobet and Prodigy are made in China. The economical Grobet USA flex shaft machine is often less than $100. The basic kit features a 1⁄10-hp motor, maximum 18,000 rpm, a standard plastic-housed electronic foot pedal, and a #30-style handpiece. 

The comparably priced Prodigy has a slightly more powerful 1⁄8-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 is more widely available. 

Chinese goods can occasionally have a less than savory reputation, but things change, and Chinese goods are improving. I would avoid flex shafts from nonjewelry suppliers or very cheap off-brands. But the Grobet and the Prodigy offer an economical alternative for anyone who is just entering the field, needs a backup unit, or will be using the tool relatively infrequently.

Other brands

Dumore, Pfingst, 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 secondary market. Craigslist, eBay, yard sales, and even newspaper classified ads 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 them new from smaller suppliers if you dig deep enough online.

The bottom line

Confused? I’ll make it simple. If you plan to work long and often at the bench or you’re looking at a career in the metals or related fields, buy a Foredom SR or an OttoFlex (Buffalo Dental). The 1⁄6–1⁄5 hp that these machines generate will be plenty (a minimum of 1⁄8 hp is needed for some attachments, such as a jump ring cutting jig). They run just under $200. If your budget is limited, buy only the machine (motor, shaft, handpiece, and foot pedal). If you can spring for another $20, buy a basic expanded kit, which includes a nice selection of burs, bits, and accessories; these provide a survey of what’s available. Avoid more extensive kits — they simply have too many bells and whistles. If you’re a hobbyist on a tight budget or need another light-duty flex shaft, grab a Grobet or Prodigy motor, shaft, handpiece, and foot pedal.

When you’re comparing prices, be sure you’re looking at comparable kits or systems. An SR machine may seem inexpensive until you realize that the price includes only the motor and the shaft!

In conclusion

Like any tool, the flex shaft ideally functions as an extension of the body. It’s important to remember that the operator is the key in this equation. Maximizing the possibilities offered by this amazing tool is a function of control, which itself is a function of practice. It takes time to master this tool. But it’s time well spent.

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