Black+Decker Cordless Rotary Tool

Tools like this are usually called a “Dremel”, after the brand that invented them. The generic name is a rotary tool: a motor with a collet on the end that spins a small bit very fast.

It does the jobs a full-size tool is too crude for: cutting a protruding lead flush, tidying the edge of a printed part, opening out a hole in an enclosure, removing a burr, polishing a contact, drilling a half-millimetre hole.

It is cordless, so it goes where a cable will not and you do not unwind an extension lead for three seconds of work.

The bits

The consumables are sorted into boxes, and there are more of them than you would think:

• Cut-off discs — thin reinforced ones and diamond ones. They cut metal, plastic and circuit boards.
• Grinding stones and drums — removing material and levelling an edge.
• Burrs — cutting a slot, opening out a hole, engraving.
• Brushes and polishing wheels with compound — cleaning contacts and finishing a surface.
• Micro drills — from fractions of a millimetre, for boards and small enclosures.

A bit goes into a collet of the matching size. Clamping a thin shank in a large collet means runout, a bit torn loose and, with some probability, a fragment in your face.

Safety

The tool is small, but its speed is very high, and that changes everything.

• Eye protection is mandatory. A cut-off disc that snags shatters, and the pieces fly in the plane of the disc — which is to say, at your face.
• Clamp the work rather than holding it. The tool will jerk the work, not the other way round.
• Do not push. A rotary tool cuts with speed, not force; pressure breaks bits and heats the material.
• Hair, sleeves and cords stay away from the spinning end.
• Plastic and circuit boards smoke when cut. Work under the fume extractor or with ventilation.
• Change bits only with the tool switched off.

How to use

1. Choose a bit for the job and a collet for the bit's shank.
2. Tighten the collet with the key and check at low speed that the bit does not wobble.
3. Start slow and go faster if you need to. High speed melts plastic.
4. Guide the tool without pressing, in short passes.
5. When finished, take the bit off, return it to its compartment and the tool to its place.

Access

The rotary tool is in the hackspace room, so a plan that includes hackspace access is required. No induction is needed, but read the safety section before you switch it on the first time.