Improving ER Collet Run-out to Near Zero

摘要

I've used ER16 and ER25 collets for many years and always been impressed with their strong grip and wide range. Their accuracy has tended to be quite good - typically 0.02 to 0.03mm total indicated runout (T.I.R.) but variable. Sometimes no visible run-out (so I don't check it) and other times I can see its not quite right and I re-assemble, usually correcting the issue. I always thought this was due to buying cheap Chinese collets. However, the need to cut an accurate width slot in one pass necessitated some concentricity investigations as 0.03mm T.I.R. was too much.