You can get .125 (1/8th) collets for a die grinder. Runout (TIR) is an issue with ALL collets and you should measure runout if you're holding a tight tolerance or, as Gerry's article pointed out, if you're running small tools.
Its easy to measure and adjust a collet's TIR if you have a little patience and use the three points method. I use this method to pick up (indicate) a bore or hole I've drilled or to pick up a tooling ball. You can use it to pick up anything with a cylindrical face or body. It takes some practice but I can indicate a hole or tool (mostly reamers) in about 2 min now.
The method; Indicate the x-axis (both sides of the tool or bore facing the x-axis) so that they are equal. Then indicate the tool on one side of the y-axis so that it equals the the x-axis you just indicated. Once the three sides have been indicated you can rest assured the fourth side of the tool is equal. Light tapping in either direction on the tool shank, based on the runout, is generally accepted for indicating reamers/drill bits/End mills.
Another tip; Only move the tool, gantry, or spindle half the distance of the TIR your indicator is reading. Then measure again. I promise if you do this in the right direction you will be very close to zero TIR on your next reading.
Good luck, I hope this helped.  |