[Atomic_]

What are the advantages the expensive bearings have over the cheap ones? Do they last longer? If so should I buy the expensive bearings once or continuously buy the cheap ones?

Cheap Bearings:
7007C Precision Ball Bearing 35x62x14
7005C Precision Ball Bearing 25x47x12


Expensive Bearings:
BNH007TU Nachi Angular Contact 35x62x14
7005CYP4 Nachi Angular Contact 25x47x12

[jalessi]

Why not use NSK? Look on eBay, sometimes they are very reasonable:

https://www.ebay.com/itm/NSK-7007AW-...ss!53142!US!-1

Your G0704 will never take advantage of 35000 r.p.m. bearings anyway.

Welcome to the Zone,

Jeff...

[RCaffin]

I don't really think you need the Nachi bearings: you are not going fast enough for the difference to matter.
The $20 ones sound fine to me.

Cheers
Roger

[Atomic_]

Would the higher rpm bearings generate less heat?

[RCaffin]

Yes, that is correct, but you would need to be up at the high end of the RPM to notice. Axis drives will never get anywhere near the high end. A few drops of oil once a year in most cases and you are good.
Spindles can if they are very high speed. For that they need to be small diameter - which is less robust. Trade-off.

Dental drills can easily clock 60k rpm. Normal service contracts are meant to replace the bearings every 6 months. My dentist told me that is what the nominal contract says, but in practice they get replaced every 3 months - with the intermediate replacements being done under warranty. That is factored into the contract price of course.

Cheers
Roger