Hey Guys,

So I just finished the belt conversion from Benchtop Precision and as part of it, I replaced the spindle bearings (roller) and the upper larger ball bearings around the barrel they recommended. Bought some of the Lubex grease that everyone is using for the spindle bearings, the barrel bearings were sealed so no grease was added. I pressed all the bearings in with my press with the exception of the upper spindle roller bearing. This was pressed in by screwing the top nut down onto it until the spindle had no play between the upper and lower bearings, then I gave it another 1/4 turn which incidentally stopped the nut as I must have hit the end of the threads. After assembly I ran the new setup at 1000 RPM increments each for 10 minutes up to 4500 RPM which is where it topped out. I went to work on my first piece and after 20 minutes of milling at 4000RPM the spindle was so hot that I couldn't hold onto it for more than a few seconds. I have an infrared temperature gun that was only picking up 90 degrees but that can't be right as the casing above it was 112 which I had no problem touching.

So, where did I go wrong? Cheap bearings? Too much preload on the spindle bearings? I used more grease than everyone on the spindle bearings but I don't think I over did it? I read that I may need to remove the bearings and re grease now that they are broken in but I hate to stress them pressing them in and out. Any suggestions?


The upper ball bearings as suggested are:

6007ZZE Nachi Bearing Shielded C3 Japan 35x62x14
6209ZZE Nachi Bearing Shielded C3 Japan 45x85x19

And the spindle bearings are:

32005 X/Q Reference speed 11000 rpm, Limiting speed 14000 rpm
32007 X/Q Reference speed 8000 rpm, Limiting speed 10000 rpm