Minimizing Extended Toolholder Runout

Troubleshooting the Pocket NC
#1

Hi all!

Recently, I’ve started working with some small diameter tooling (> 1mm) and I’m struggling to minimize the runout of the extended toolholder. Before I tighten the collet holder, with the collet firmly inserted, I’m seeing about ± 0.0002 of an inch of runout on the end of the tool. Once I tighten the collet holder firmly, I see all the way upwards of ± 0.00065 of an inch. This is with the supplied 1/8" collet–the effect can be even more pronounced between different 1/8" collets. Any thoughts on what may be causing the collet to shift off-axis as the holder is tightened? I’ve inspected the threads on both the extended tool holder and the collet holder, and both appear to be undamaged.

Thanks!
Stephen H

#2

After repeating the same experiment with the shorter tool holder, I’ve discovered that if I pre-insert the tool into the collet before screwing on the holder, there’s an internal ridge that prevents the collet from sitting flush against the front of the collet holder! Hopefully inserting the tool after the collet is flush with the collet holder will prevent this from happening

1 Like
#3

I’m even surprised about the accuracy you have. All of my toolholders are about +/-0.025mm (+/-0.001 inch) off-center. Some are better and with them I use < 0.5mm tools. My general part accuracy with brass or alu is not better than 0.1mm.