Correcting spindle run-out

I thought I’d post this for others using very small bits in the Nomad where run-out can be an issue. If you’re suffering frequent breakage this may be of interest.

I checked three 1/8" shank bits and found the run-out to be about 0.06 mm, a serious amount as I’m preparing to use a 0.127 mm bit. I also measured run-out of a bit in a high precision 1/4" collet and found that to be about 0.03 mm. I’ve ordered another, high precision, 1/8" collet but thought I’d see how much of the run-out might be in the spindle itself. I found the spindle run-out, as measured on the threads as well as the smooth area just above the threads, to be about 0.03 mm. This appears to explain the run-out with the higher precision collet (purported to be precise to 0.0002" = 0.005 mm).

I loosened the screw holding the spindle in place with the intent of applying a bit of torque to allign it. This turned out to be unnecessary, when I simply retigntened the screw the run-out was reduced to about 0.005 mm. Easy peasy except for the fact this screw is seriously torqued down, it was a little unnerving to loosen it.

I’ve yet to receive the new collet so have yet to comment on the efficacy of this adjustment but my dial indicator is liking it.

EDIT: After testing with the new collet, the run-out, with bits installed, remains under 0.005 mm.
EDIT 2: My first run with a 0.20 mm bit in 145 copper after the new alignment, flawless.


If you are doing high precision work you may need to install the bit and check runout and if too high loosen it and move it and re tighten and recheck the run out. On big mills this is a part of tool set up.


Interesting. Perhaps the clamping was distorting the spindle cartridge.

@PhilG I suspect it was just mis-seated in the carriage. Being amplified by the lever arm between carriage and collet threads, a micro amount of mis-allignment would explain the run-out.


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