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View Full Version : Lathe spindle bearings, checking/adjusting ?



old blue
04-11-2009, 02:00 PM
I have a ? on how to check and adjust if necessary the spindle bearings on
a lathe. I have run lathes for almost 20 years but never done any maintenance on them. I have my own now and would like to know the process.

thanks old blue

nheng
04-11-2009, 03:45 PM
Regardless of the type of bearing, you want smooth operation and no bearing noise. On a ball or roller bearing spindle, if you think you hear noise you can check with a long screwdriver, handle to the ear, tip to an area near the spindle end that you are NOT GOING TO TANGLE WITH.

If you have ball or roller bearings, proper preload affects the lathe behavior and will show up in the finish, chatter, etc. if it is loose. Preload can be checked coarsely with an indicator on the spindle nose end while you push or pull the spindle axially in or out. You can also check for any play radially by pulling up or down on the spindle nose while indicating that.

Lastly, if you need to adjust preload, the most common method (if not spelled out by the maker) is to let it run at moderate speed for about 20 minutes. There should be some temperature rise but it shouldn't be hot. I've seen figures of (I think) 120F for a Rockwell lathe, others mention "warm to touch". Some may spec an end play when it is cold and self compensate when it heats up. Preload is usually adjusted by means of a spanner or other type nut on the back end of the spindle. There's usually some locking method like a setscrew so remove that and give only slight adjustment before checking it again.

Another method for testing preload on some machines (called out by Emco support several years back), is to give a normal size chuck a quick, hard snap with a finger (gears in neutral). If it spins about 1 - 1.5 revolutions, you're pretty good. This is done cold with gears disengaged.

For South Bend lathes with solid cone bearing sets, play can is adjusted by shims/tightening of the bearing caps. I'll leave that for someone else to get into. "Play" numbers are on the web and should be measured with proper lube in place.

Den

old blue
04-12-2009, 09:11 AM
The spindle has a ball bearing at the rear and roller bearings in the
middle and the front. When you spin the spindle by hand you can
see and hear loose rollers in the middle bearing. I did check with
a indicator, i got about .0003 to.0005 end play. Will I need to
tighten this up?

thanks old blue