Hey guys, I’m sure this topic has been beat to death, but I’m not finding the exact info I’m looking for. But I just finished retrofitting my cnc, and while I’m in the flow of upgrading everything, I’d like to replace the tapered roller bearings in the spindle to something like angular contact bearings so I can run the spindle at a slightly higher rpm since I’d prefer to use carbide endmills wherever possible. The max rpm my machine is currently rated for is 4000 rpm which obviously a bit low for a lot of carbide, so I’m wondering if changing the bearings will allow enough of an increase in rpm to be worth going through the effort of rebuilding the spindle? Or if I should even attempt an “unnecessary” spindle rebuild, because I’m aware of the hazards associated with precision spindles and contamination. So question 1, is it worth the risk/hassle to rebuild a perfectly good spindle? Question 2, are angular contact bearings the correct choice for my application? And question 3, how much faster could I potentially run my spindle if I do replace the bearings? In case these factors have an effect, the head of the mill is like the vari-speed Bridgeport heads. It uses a belt drive to a “bull gear” I guess you’d call it, to spin the spindle gear, which has a hi/n/lo selector. But I change rpm through the vfd, not the varispeed controls Any info would be appreciated. Thanks !