Mill spindle bearings

JTknives

JTknives

Blade Heat Treating www.jarodtodd.com
Knifemaker / Craftsman / Service Provider
Joined
Jun 11, 2006
Messages
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As alot of you know I picked up a nice old enco bench top mill and have been fixing it up. I have got the ways all cleaned and the gibs adjusted which left me with around .007-.012 backlash on the x and y. I then decided to greese the spindle bearings and what I uncovered was a bunch of hard soap like stuff caked on the outside of the bearings. So I pulled the spindle and removed the bearings. Mose mills I have worked on took a cartage for the spindle bearings and everything was sealed and pre tensioned. If you had a problem you sent the spindle cartarge in for rebuild. Well this uses 2 tapered roller bearings and I don't mind as it's easier for me to work on and not a 3000-5000 spindle rebuild.

But here is my question I'm going to replace the bearings as one of the bearing races has some crosion and the race does not match its mating race. By that I mean the letter stamp so I'm guessing it was replaced and thy could not get the race out of the spindle so thy just replaced the roller part. The lower bearing is also a tapered roller bearing and looks in good condition but I might as well replace it as well. The bearings are NSK Japan with the numbers
HR30205J and HR30206J

There is no tolerance "class" on them and I don't know enough about bearings to know if the replacements will be better or worse. A quick eBay search brings up a bunch of them for cheep but are thy the same or a lower class. Should I stay with NSK or go with another brand like timken or SKF. I looked briefly at SKF and instantly noticed made in Mexico on the bearings so I wrote it off. I know there has to be someone out there that knows more about bearings then I do ;). Looking for any advice I can get on what I should put in this mill, thanks guys. I will upload some pictures of what I pulled out.
 
JT ,I don t think that tapered roller bearings have tolerance "class" . They're all good NSK ,NTN ,FAG ,SKF ........ Just be sure when you mount them and tighten , roller inside must roll not slide . .. .
 
Tapered roller bearing are different then normal bearings and do get that rating. Thy do have a rating but I can't seam to find bearings with higher ratings.
 
I don't think you will, as I think that specific bearing is mostly meant for wheel bearings, and there are not any precision designations for it. That's just a guess though.

I would go with NSK. Being tapered and preloaded I'm also not sure the difference between a "standard" and "precision" would actually be determinable on a manual machine at the speeds and feeds they're normally operated at. Where if they were simply ball bearings like some drill presses the higher precision ones become necessary because they can't be pre-loaded against axial run out.

But, I don't know that I would have replaced them anyway if there wasn't measurable run out or axial play. Cleaned them up sure.
 
Going through this myself on a benchtop horizontal mill. 07098 Timken's are what I am seeking. Timken seemed to say that Class 2 was their precision bearing,, but I'm having a hard time finding a "specific" rating as well.
 
Before I took it apart I was getting about .0003 TIR and the spindle was tight. Trying to move it by hand with a lot of force only moved it maybe .0005-001. I just figured since I got it apart I could put new ones in. Like I said the lower bearing does not look bad but the top one looks like it might have got water in it as it was some etching on the race and a few of the rollers. But to just replace them with the same NSK bearing is like $15 each so I might just do that.
 
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Oh, that's not too bad at all. I was thinking they'd be more.
 
Yeah I looked over that PDF last night, NSK has one like it as well. But it left me with more questions like how do I tell what class the bearing is. There is nothing stamped on it besides the bearing number and a F.
 
Ok that's funny right there
 
JTknives said:
Yeah I looked over that PDF last night, NSK has one like it as well. But it left me with more questions like how do I tell what class the bearing is. There is nothing stamped on it besides the bearing number and a F.
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Just bye like the same one you already have :) Did you look in numbers in PDF ? -0.00047 on inner ring bore is standard bearing class .
 
I've always liked NSK bearings myself. Last ones I got were made in Poland, but they're still as good as anything else I've used. Them and SKF are my go to
 
kuraki said:
I don't think you will, as I think that specific bearing is mostly meant for wheel bearings, and there are not any precision designations for it. That's just a guess though.

I would go with NSK. Being tapered and preloaded I'm also not sure the difference between a "standard" and "precision" would actually be determinable on a manual machine at the speeds and feeds they're normally operated at. Where if they were simply ball bearings like some drill presses the higher precision ones become necessary because they can't be pre-loaded against axial run out.

But, I don't know that I would have replaced them anyway if there wasn't measurable run out or axial play. Cleaned them up sure.
Click to expand...
I used NSK bearings on my CNC. wonderful creatures they are.
 
ABEC is a motor bearing classification that got applied to all sorts of things. I don't know if taper roller bearings are one of them.

ABEC 7 super precision are the standard go-to for a machine tool spindle. You can get higher, you can get lower, but that's where most folks gravitate. I certainly wouldn't use ungraded or less than ABEC 3 on a mill. ABEC 3 or ABEC 5 might be ideal for this application.

Machine tools such as mills use a precision spindle bearing layout and frequently have two radial bearings (deep groove or similar) at the nose that are preloaded against each other and something else at the other end that accommodates some float for thermal expansion. On a big mill that sees large loads, high speeds, and needs high precision the cost for the bearings themselves usually total around $1,000-$3,000 plus all the other stuff that goes into a spindle rebuild. The bearings on a small mill might only total a couple hundred dollars. A bearing that costs $15 does not belong in a machine tool, it's intended for an application that tolerates a little run out.
 
I did not want to spend $15 on a bearing for my mill. It's a small 500lb enco bench top mill and thoes bearings are what's listed as it's replacement. Thy do have different classes of tapered roller bearings but I can't seam to find them
 
I really wanted to use a
Fag 7206-BXL-2RS-TVP
And
Fag 7205-BXL-2RS-TVP

But hard to find and a tad bit more pricy at around 10x the price.

If I drop the XL and just get the
Fag 7206-B-2RS-TVP &
Fag 7205-B-2RS-TVP
Thy are like $60 and much easyer to find.

Thy are an angular contact deep groove bearing. So much less surface area then the rollers so a lot less heat. But the big thing is thy are sealed and designed to be used in pairs and under compression. Thy are can be run faster which is a nice thing.
 
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