[Uguessedit]

Not a bad price for those Nachis. I’m looking at $150/or for AC in a P4 abec 7 grade. Have to buy same pairs so it’s good I have several mills.

Old post but I am curious if anyone has doubled them up too. Also the very top two of the four deep groove seem to be standard abec 1 quality on all my mills and wondering if anyone upgrades those? Especially given a belt drive conversion it seems abec 3 is the way to go since nothing better is available out there right now in a standard deep groove. Obviously ac bearings won’t work where they can’t be preloaded. I blew a seal on one of my mills so I figured I’d change all the seals and bearings. I might even make my own belt drive if time allows.

[Uguessedit]

I have got o know how you used these cheap angular contact bearings. I Do sides Labeled “B” face each other since that is the high lip of race? After installing dry I have .007 run out and I haven’t even ran it yet. I’m a little concerned about using these.

Hi guys,
While working with my machine today the lower spindle bearing started to heat up pretty good. I was on borrowed time with the belt conversion running 6500 rpm and stock tapered roller bearings.

My question is about angular contact bearings for the spindle. It is my understanding that in a perfect world one would have a double set of AC bearings at the bottom of the spindle with a single regular bearing at the top. This eliminate the thermal expansion messing with the pre load I guess.

So on our less then perfect machines (RF-45 types) do you simply replace the tapered roller bearings with AC bearing (one on top and one on bottom) and get the pre load as close as you can? Or have you guys been machining out the lower spindle for a double set of bearings at the bottom?

I am looking at:

7207BMU Nachi Angular Contact Bearing 35x72x17 Brass Cage C3 Japan Ball Bearings... $40.00 each.

Or

7207 Nachi Angular Contact Bearing Steel Cage C3 Japan 35x72x17 Ball Bearings... $23.00 each.

Thank you for your help.

[mattinaustin]

Bringing this oldie back from the dead, did you ever figure out which sides of the AC bearings face each other? I am guessing they should be opposite each other. I'm thinking the bearing label is facing outward from the spindle? In the picture I am showing the upper bearing facing the way I think it should. Can anybody validate this? Thanks!
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