Which Bearings Do I Use for Mill Spindle Rebuild??

[Utah Smitty]

I'm in the middle of rebulding the spindle on my Rutland (Kao Fong) vertical mill. I've ordered the pulley and intermediate bearings, but I'm having difficulty knowing which grade precision bearings I need for the spindle itself. They are a pair of 7207 angular contact bearings with open sides (no seal or shields) since the lubirication is a total loss oil system, not grease.

My specific questions are:
- What ABEC class precision should I use?
- What contact angle should I use?
- Does anyone have recommendations as to brands to avoid??

Thanks,

Utah Smitty

[warmstrong1955]

ABEC 7 would do it.

I would think 15 or 20 degree. Not sure what is available in the 7207. Standard is probably about 40.
Lower the angle, the better the bearing will handle axial loads. I think Bridgeports use 15 degree....several here will know.

For something like a mill....I'd spend the money.....and avoid any cheap stuff at all.
ABEC 7's will damage your wallet compared to ABEC 3's by the way. Precision comes at a price.
US, Japan, or Germany. SKF, Timken, NTN or FAG....good ones, and you can't go wrong with any of 'em. There are several other names that have been consumed by the 'Bearing God's, (which would be Timken & SKF) so don't toss out names like Torrington or Fafnir, who were also were good.
I hear Nachi is not bad....made in China....but I have no experience to validate that, at least with precision stuff. Used some in electric motors & things, but only ABEC 1 or 3.

Bill

[Utah Smitty]

Thanks, Bill--good informaiton. I was especially unsure about the contact angle... it seemed to me that 40 degreees would be better, but I had heard of people using 15 degree angle bearings so I wasn't sure which would be best.

Regards, Smitty

[wlw-19958]

Hi There,

Contact angle will depend on the type of load the spindle will
be subjected to. As the contact angle increases, the more axial
load the bearing will handle. As the contact angle decreases, the
more radial load the bearing will handle

Milling machine spindles are subject to both kinds of loads. Usually,
they are subjected to more radial loads than axial. So, I would say
a contact angle of 15° to 25° would be right in the neighborhood.

Good Luck!
-Blue Chips-
Webb

[Utah Smitty]

Thanks Blue Chips--

Now I understand the reasoning behind different contact angles. I was able to find some ABEC 7 bearings with 20 degree angle at a decent price, so I ordered them.

General Question to All:

Even though these are oil-lubed bearings, should I put a light coat of grease--white grease, etc. on them before installing?


Thanks,

Utah Smitty

[Glenn Brooks]

There are a lot more knowledgable people here than me, but I would never grease a bearing used in a dedicated oil lubrication system. The grease will prevent proper lubrication in the bearing and may/will eventually dilute out, leaving the residue to accumulate somewhere else where you may not want it go.

[warmstrong1955]

Regular grease....no.

Something like Lubriplate 105, or other low viscosity assembly greases....yes.

Not a lot...a little....and makes up for that delay of the oil gettin' there....and washes out when the oil does get there.


Bill

[Utah Smitty]

Regular grease....no.

Something like Lubriplate 105, or other low viscosity assembly greases....yes.

Not a lot...a little....and makes up for that delay of the oil gettin' there....and washes out when the oil does get there.


Bill

Okay, thanks to both of you. My old bearings were greased, on the bottom 2 sets, which is probably why they failed, but on the other hand, I didn't want to start up a dry bearing...

Thanks for the input,

Smitty