Bearing break-in procedure?

[websterz]

I just finished installing tapered roller bearings in the headstock of my lathe.    Is there a recommended break-in process that I should follow? 

[Stilldrillin]

I have done both lathe and mill......

I nip up adjustment ring, until there's no movement in spindle. Then run free for a few minutes.....

Then repeat, running free.

Then repeat, and do some gentle machining for a few minutes.

Then check again for movement.

I prefer to have nill preload in these underpowered machines...... 

David D

[Country Bubba]

I recently had to replace the bearings in my mill/drill and here is information I found on breaking procedure:

Typical run in for spindles is a starting point of about 400 rpm, 
up to max in 500 rpm increments, in steps of 30 - 45 minutes. 
Check housings for excessive heat as you go.
Then reverse and do it over!
Watch temprature. If it gets hot, stop let cool and do over.

The Fafnir Superprecision Machine Tool Bearing catalog suggests that with optimal design,
 bearings running synthetic low friction grease ought to be able to run about 20 degrees C
 over ambient or about 40 degrees F. In fact, they suggest a proper break-in procedure temperature of 130 degrees F.
involves running the spindle until it reaches 150 degrees F, turning it off to cool, and repeating the cycle
until the spindle stabilizes at 130 degrees F or lower operating temp.
The ideal equilibrium operating temperature is 95 to 115 degrees F. Maximum temperatures should not exceed
170 degrees F. Timken's published specs for tapered roller bearings, including bearing life specs, assume an operating
temperature of 130 degrees F.


HTH