[Runner4404spd]

you may not have enough grease in the bearings. also the bearings will take a seat on the races and loosen up the close tolerances that were set. you might need to snug them up again.

[Chris D]

I have not worked on the spindle for my mill yet, but I suspect that the bearings are grease packed and not oiled. As such, after confirming this, you will need to pull those bearings back out and pack them properly with grease or they will fail pretty quickly.

Packing bearings with grease is a bit of a pain and it needs to be done correctly. Simply wiping them with grease is not the correct way. There are two methods I am aware of to pack bearings:

1) Pnuematic unit that forces the grease into the bearing under presure. These units can be purchased and can be costly.

2) The old fashioned way I learned way back in high school. Assuming you are right handed...

Place a glob of grease in the palm of your left hand

Hold the bearing in your right hand

Using a sort of scraping motion, force the edge of the bearing into the grease glob while pushing it towards your palm. The grease needs to enter the bearing at the ends of the rollers. As you push the bearing into your palm, the grease if forced in between the rollers. You continue to do this till the grease comes out the other end of the roller (and cage). Then rotate the bearing and repeat the process. Continue untill you go all the way around the bearing.

It takes a while - perhaps as much as 5 to 10 minutes to pack a bearing this way, but it is the only way I know of to make sure you get the grease inbetween the rollers and inside the cage where it needs to be. Just wiping grease against the rollers is not suffficient.

As for pre-load, this is something you will tweak a bit during the first couple of hours of running. The bearing should not get hot, it can run warm though, especially at high RPM. The temp difference between hot and warm is approximately

160 degrees F or more = hot
140 degrees F or less = warm

These are relative to touch and are approximate.

Chris