10K Spindle Bearing Temperature Rise: How Much is Too Much?
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  1. #1
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    Default 10K Spindle Bearing Temperature Rise: How Much is Too Much?

    After trying to sell my 10K for several weeks with no serious offers, I decided it probably wasn't selling for what I though it is worth because it was mounted on a couple sheets of plywood on a floor dolly and it still had years of grime on it. I built a bench out of 2 1/2" x 3" hardwood boards I've had stickered up in my basement for years, and used a 1 1/2" thick pine top that I got from a guy at work. I finished cleaning and reassembling it this weekend, and have decided to keep it .

    Before:

    img_7518.jpg

    This Morning:

    img_7655.jpg

    I checked the spindle bearing clearance this morning, and found the front bearing has 0.002" clearance and the rear has 0.005". When assembling the headstock, I made sure that the bearing retainer screws were loose and used a torque wrench to tighten the bearing cap bolts to 10 ft lbs based on the rebuild manual's recommendation of using approximately 20 lbs of force and a 6 inch wrench. I then tightened the retainer bolts using just my thumb and forefinger on a stubby flathead screwdriver. The bearings and spindle journals looked flawless when I cleaned them, and the indicator I used is older and not as responsive as I would like, especially in my unheated shop. So reading that too much clearance is better than too little, I decided to run the lathe for an hour at maximum spindle speed and check how the bearings heat up. I used an infrared thermometer to check each bearing temperature every 5 minutes, and below are the results.

    screen-shot-2019-12-01-3.10.05-pm.jpg

    Does anyone have any experience with how much temperature rise should be expected? Since the temperature rise was almost 35 deg F over the hour on the (tighter) front bearing, I'm nervous to remove any shims, especially from the front bearing. The mass of the headstock is pretty large, and I would assume that a lot of the heat being generated is being wicked away from the bearing and not showing up as an increase in temperature. I definitely don't want to go chasing the spec only to mess something up, especially if I'm not confident in the clearance measurements to begin with. I also didn't notice any significant drop in oil level in either oiler, and the surface finish on the aluminum collars I turned to align the tailstock was excellent.

    Any advice would be greatly appreciated as I have no idea if the temperature rise I saw was normal. Thank you!

    -Keith

  2. #2
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    Nice lathe.

    Usually with bearings like these, you will see a problem where the spindle bogs down or even stops, when run at extended
    time at top speed. This is typically accompanied with the bearings getting 'real damn hot.'

    That your spindle ran fine at top speed, for an extended time, and the temperature stabilized at a reasonable number, implies
    that the setup is in good order.

    I've never been able to get plain bearing SB spindles to run at top speed, with the specified clearance, unless I replace the
    spindle oil with 0W30 mobil one synthetic engine oil. Otherwise they do tend to bog down and slow up.

    I would leave your setup the way it is for now. Some day you might want to slightly reduce the clearances a bit. If the lathe
    works well, however, maybe not.

  3. Likes michiganbuck, Dobermann, USNmechanic liked this post
  4. #3
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    Thanks Jim! That advice makes me feel better about leaving it for now. I was mainly concerned that at some point too much clearance could be just as bad as too little. Someday I may remove one layer from the rear shim and repeat the test, and then compare the results. I’ll be sure to post them if I do.


    Sent from my iPhone using Tapatalk


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