Ring mandrel

A ring mandrel is a tapered rod, usually metal or hardwood, that gradually increases in diameter along its length and is marked with ring size lines. Slipping a ring or a length of wire onto the mandrel and sliding it along the taper shows exactly what size it will be once finished.

It matters for anyone making wire-wrapped or shaped rings, since it gives a consistent, repeatable way to size a ring rather than guessing, and lets several rings in a batch come out to the same true size instead of varying slightly from one to the next.

When buying, metal mandrels hold up better to shaping pressure than wood or plastic ones, and clear, engraved size markings are easier to read accurately than printed ones that can wear off. A common mistake is hammering or forcing a ring too firmly against a mandrel not designed for shaping work, which can bend the mandrel itself or stretch the ring past the intended size.