I just finished replacing the spindle bearings for the first time, and it made the shortcomings of the current system very clear. The mill currently uses 6206 deep groove radial bearings both on top and bottom. The bearings are a press fit both on the spindle and the housing. Bearing preload is set via a nut on the end of the spindle.


The problems I see are:
1. Since the top bearing is a press fit on the spindle it makes preload difficult to set.
2. Deep groove radial bearings, while adequate, aren't ideal for a mill spindle.
3. Having a press fit on both the spindle and housing makes it more difficult to replace bearings.


After researching and reading a lot of the NSK and SKF catalogs, I think my best option would be:
1. Sand/polish the top bearing seat on the spindle to take it from a press fit to a tight slip fit.
2. Use Belleville washers to to exactly set my bearing preload. My only concern is a heavy cut might overpower the Belleville washers and pull the spindle down, but I doubt the actual forces at play in my mini mill could excert that much force. Alternatively, I could continue to set the preload using just the nut.
3. Upgrade both bearings to angular contact. I'd need to find a way to seal the bearings or re-grease them on a schedule. I did find sealed angular contact bearings online, but they're generic Chinese: Angular Contact Ball Bearings - Arc Euro Trade


I was wondering what you thought of my plan, and if you had any suggestions or advice. Thanks!