[rickj55]

Hi, I have inherited in the shop a SS20 that has only run plastic before. I now run aluminum, SS & T1 titanium. The machine is always run in chucker mode for reasons beyond this thread. I run with a 6ft bar feeder and 3/4 rod. The problem I am having is on the main spindle the collet nut comes unscrewed mostly when I cut the harder materials. Yes I know the nut just bottoms out, the collet is open when the nut is tightened, the nut IS TIGHT when tightened, everything is as it should be when this is assembled, I have 45 years of mechanical xp. I should also say this 5 year old machine has been beat on by well you know. Currently I have to put med strength loctite on the threads during assembly and this helps but sooner or later that fails. I also regularly hold .001 tolerance. There is a sleeve in the spindle large enough for the bar feeder pusher rod but this could probably be smaller as I still get some bar whip. I also do knurling on it which seems to be the worst. Other than the knurling I am not really putting l a lot of radial load on it during turning. I think that covers the situation. Anyone have any ideas why the collet nut is coming loose?? I have talked to Tsugami reps and they have never heard of this, say it shouldn't be happening, and don't know why it is.
TIA

[DCogswell]

Have you tried a new spindle cap nut? Also, have you tried converting back to guide bush mode and see if the cap is still coming loose?