A clamp immobilizes the handpiece so that it becomes a stationary workstation. You can find several handpiece clamps out there, usually two blocks of plastic that grip a #30 handpiece. Some have hardware that clamps to the bench, while others are themselves clamped between the jaws of a bench vise.
It’s tempting to start adding attachments to your flex-shaft arsenal and not buying more handpieces. After all, you only really need one #30, right? But in practice, disconnecting the handpiece from one attachment and attaching it to the next can be a pain, especially in the heat of the metalsmithing moment. It’s ideal to have a flex-shaft consigned to each attachment, but who can lay out the cash? (Although, I highly recommend dedicating a machine to the drill press.) A decent compromise for the mobile attachments — angle grinder, wax trimmer, etc. — is to have a #30 hand-piece for each; the assembly can be switched out like you would any handpiece. To the light user, this may sound excessive; but for a professional, where time means money, it’s a good investment.
Shared foot-control panel
If you do have more than one flex shaft, and you’re using multiple foot controls, this gizmo is calling your name. You can use up to five machines (one at a time), all with 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. Any motor that can be used with a foot pedal will work with this switch. Otto Frei’s the only supplier I can find who carries it.
It doesn’t seem right not to mention the tool that could be seen as the evolutionary legacy to the flex shaft. With the motor contained in the handpiece and no shaft to weigh you down, the micromotor is similar to a Dremel. 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, and adjustable chuck and quick-release handpieces. Some offer hammer and specialty handpieces — even belt-sanding attachments. Performance varies widely, so do your research!