[Jim27]

Have a servo products desktop CNC mill with WW collets. Have done some milling of aluminum and even a bit of steel (not much and very light cuts) and haven't noticed this issue. Routing some cherry with a 1/4" straight router bit and it keeps walking out of the collet increasing depth of cut until the spindle stalls or I stop it. I found the torque of 25 in-lb limit and degreased the shank and inner surface of the collet. The surfaces look good. The bit shank is as close to 0.25 as I can measure with dial caliper - maybe 0.0249. Tightened collet to about 18 in-lb - I suppose I could go more but the hardware is pretty small and that seemed like a lot. I do have a lot of tool stickout. The collet is only about 3/4" deep and the tool extends almost 2" beyond the collet. Cutting length is 1". I could cut down the shank about 1/2" to reduce stickout. I think the issue is the collet design only clamps at the tip of the collet and the shaft is able to deflect slightly in the collet and this deflection slowly walks the shank out - just a guess but the best I can come up with. It's a straight flute tool so the cutting shouldn't be causing any pullout force. I am at a loss for what to do other than reduce my depth of cut. It's current 0.125" which seems to be well within the power capability of the spindle if I could keep the bits from creeping out.

[Jim27]

I reduced DOC to 1/16, used a slightly shorter bit, tightened everything up and it ran smoother and without pullout. BTW, running 16"/min. Need to set up a vacuum brush to keep the chips up and keep from recutting - think that made the issue worse. For now I just followed the bit around with a vacuum.