Yes your spindle is getting to hot, it should not get any hoter than *100 to *140f.

I would back the preload off. It may be best to back it off enough that it does not cause much heat at all ( all though being tight enough not to have any clearance). Break it in all the way up to high speed (with the lighter preload), then add preload a very little bit at a time until you reach the temps I meantioned. Each time you tighten preload it will require breaking in at all speeds again. It may gain temp, but as you run it the temp drops and stabilizes. WHen it stabilzes at the right temp yuor preload shuold be good. Now you have to use good judgement when doing this, the spindle will always need to fill smooth, without to much of a tighened feeling. In other words if you tighten it once, and the heat stays low but the spindle feels to tight it may be to tight. One of the best ways of disscribing the feel is, it will feel like the spindle is being turned in super thick oil/grease. It will have a drag, but be very very smoooth. It should not take extreme force to break it loose when yuo start to turn it by hand, although it should not freewheel easy either.




I know doing this way will be very time comsuming, but it works. Using a infrared temp gun would really help here. It is normal for it to gain temps when you tighten preload 9at each step), but not to the point it gets to hot to touch. It would also be best that after each preload ajustment, and run in is preformed, you let it cool and then run it again to record the heat and make sure nothing changes. When yuo reach the proper heat range, and it repeats the same temps after a cool down, then its time to run it at high speed for a long duration of time (maybe 1 hour) to insure all stays stable. AFter a 1 hour run in if it cools off to much then a very small bump in preload may be needed, but not much. You dont want it to run to hot, but to cool shows not enough preload. Now getting it to hot can kill bearings, so this is why its best to start low and work your way upto the right load/temp. If the bearings get hot enough to change color you may as well replace them because its to late.


BTW, nice looking machines, good luck.


Jess