Hello from a new member. I work in a small factory and have recently been given a new task of measuring a variety of small molded parts with a micrometer. I have plenty of experience using a micrometer with metal parts, but not with plastic, and we seem to have some disagreement among the staff about how it should be correctly done.

A standard micrometer has a ratchet on the handle so that when you close it it will "click" onto the piece, the click-ratchet ensuring that the same pressure is applied every time. (This way, a heavy handed person won't squeeze too tight and a light handed person won't squeeze too soft -- all users will end up in theory with the same measurement.)

At least that's how it works with a solid metal part. Some people I work with think that with plastic parts, which have a tiny bit of give to them (ABS plastic), you shouldn't use the click-ratchet, but should just close the micrometer until you can "feel" it touch the part. I do understand what they are saying, but it seems to me this is guaranteed to introduce a lot of variation into the measurements, with different people getting different readings according to how light or heavy their touch is.

Is there a standard "best practice" for measuring small plastic parts with a micrometer? Or maybe a special attachment to address this issue? (As I said, we are a very small company and there aren't a lot of technical people around -- we're mostly self-taught.)

Pointers or links will be welcome. And if the admins think this belongs in a separate quality-related forum I'll be glad to move it.

Many thanks.

"PeterP"