Spindle bearing adjustment

[3strucking]

I tightened up the tapered roller bearing on the chuck end of the spindle. It really helped out when parting. How do I check the far end of the spindle to see if I need to tighten up the bearings there? The manual only shows the bearings and doesn’t offer any information on adjusting them.

 

[projectnut]

I'm not sure what brand machine you have, but for most older American machines there isn't a spec as to how tight the bearings should be. Rule of thumb from John Knox (former Sheldon engineer) was to mark the current position of the fastening nut. Tighten it approx. 10* and run the machine for 15 minutes. Feel the bearing housing. It should be warm to the touch, but not hot. If the temperature hasn't risen from the ambient tighten another 10* and repeat the run time.

The bearings and housing on my machine are a bit difficult to get to, so rather than rely on my sense of touch I use an infrared thermometer. They are available from almost any big box home improvement store. Home Depot has a couple dozen models ranging in price from around $25.00 to over $200.00. Even Harbor freight has a couple from $15.00 to about $45.00.

 

[3strucking]

I checked the front bearing after I adjusted it. It was warm but not hot after one hour of running. Temp was 90 degrees using a IR thermometer. I don’t know if I should tighten up the rear also?

 

[projectnut]

Both bearings should be approximately the same temperature +/- 5*

 

[3strucking]

I will check the rear temp as I have not done that yet.

 

[tailstock4]

I checked the front bearing after I adjusted it. It was warm but not hot after one hour of running. Temp was 90 degrees using a IR thermometer. I don’t know if I should tighten up the rear also?

On most lathes I’m familiar with the back bearing, meaning the one at the back of the headstock, is usually free floating. There is no adjustment. The outer race of the bearing usually isn’t captive, and this allows the spindle to expand or contract with temperature which keeps the thermal expansion from changing the preload on the front precision bearings.

 

[3strucking]

I tightened up #4 on the schematic. It states #5 & #6 can be adjusted. I am attaching a image of the pages out of the manual.

 

[3strucking]

The lathe is a ProfitMaster sold by summit machine tools in 1983.

 

[tailstock4]

That’s an interesting one. It looks like maybe the spindle is allowed to expand from the front rather than the rear. I also think a little adjustment would go a long way. If it were mine, I would be fairly conservative.

 

[3strucking]

There’s 14 degrees difference between the rear and spindle. I don’t think I’m going to worry with the rear bearing adjustment since that doesn’t seem like much to me.