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ABEC 3 bearings for BP Spindle?

Polaraligned

Hot Rolled
Joined
Jan 28, 2007
Location
Northern, NJ
I have a Fafnir JM207K PRB DB matched set of ABEC 3 bearings.
Any reason not to use these for my 2J head spindle?
Machine is an occasional user and heating should not be an issue.

Also, what way to install them- thrust faces of outer rings together
or non-thrust faces of outer rings together.

How about preload? Matched sets usually have some built in
preload. How do I know if these bearings have the correct
preload, or does it not really matter.

Thanks,
Scott
 
I just bought a set of the same bearings :) initially having the same thoughts ... spindle bearings for cheap.

DB signifies back to back mounting. The preload is built into the bearing and is correct when the bearings are back to back or mounted with perfectly matched spacers. It sounds like some BPTs have matched spacers and some older ones may have had some bastardized custom fits.

The ABEC-3 bearings have a radial runout of +/-0.0003" while ABEC-7 is 0.00015" There's more to it than that though. I have concerns over the bore ID as well as the outer race OD. They are looser on the ABEC-3. How much trouble this could cause is not something I want to experiment with.

The J prefix indicates more internal clearance than normal. While I understand what this means, I'm not clear as to the impact on running performance or preload.

I've thought about using them for the upper pulley bearings instead. They are well suited to that but unfortunately do not have shields to retain grease and keep out dirt.

What I find funny is that the box they came in (Fafnir, gold metal foil, super precision) has markings in felt tip for the Bridgeport spindle bearing part number. It seems that someone was using if for this. Den
 
I just bought a set of the same bearings :) initially having the same thoughts ... spindle bearings for cheap.

What I find funny is that the box they came in (Fafnir, gold metal foil, super precision) has markings in felt tip for the Bridgeport spindle bearing part number. It seems that someone was using if for this. Den

This bearing number is the exact bearing that is on the current spindle. Not to say that someone put a less expensive bearing in at one time in the past. I did not use the machine with these bearings so I have no idea how well they performed (runout). The spacers are exactly the same on my spindle. Because the bearings are radial, both sides look exactly the same and I would have no idea which way to install them for proper preload. There is no "thrust" labeled side like on many Fafnir 2mm series bearings.
I am more concerned about preloading and spindle runout than the ID and OD tolerances.

I do have the proper Barden ABEC-9 angular contact bearings on hand but was thinking about saving a few bucks using the JM207's


Thanks for the input,
Scott
 
You guys are not making sense.
Gold Foil bearings, are not class 3
and any bearing number with a 2mm prefix designates precision status
Are you reading the numbers right ? and are the bearings in a sealed package together ?
Class 7 and 9 are more than just runout as you know
if they are precision bearings, they would have a copper dot or engraved X to designate high point.
Rich
 
"Because the bearings are radial, both sides look exactly the same..."

You just told me those bearings will not work in your bridgeport spindle.

Jim
 
Rich, Not to confuse this with the OP but my bearing set, same number, also has an Fxxxx (can't get at the number right now) "customization" suffix.

The J prefix is extra loose internal internal fit, the single M is ABEC-3

Polaraligned, I believe the set I have is fully marked and will shoot or scan it tomorrow and post here. That may help you to ID the sides.

Incidentally, without the 2MM prefix, it seems like these are not even angular contact but I'm not sure about that.

OT - I have a BPT bearing headache. Last week, searched on line for bearing numbers for the 1HP BPT original motor and ordered some from MSC. They arrive, I pull it apart, wrong size bearings :eek: Order the right size this time, take the motor apart today, the rear bearing is a different size :eek: I suppose the old adage "hast makes waste" still works. Don't know if I've taught that one to my kids. :)
 
Here's a scan of the marked side of my bearing(s) (not the OP).

fafnir_jm207k.jpg
 
Gold foil as in the box? Certainly these are in an originally labeled Fafnir gold foil box. The label clearly states ABEC 3.

I took a close look at the bearings and they have alignment marks on the outer race. I was wrong saying there was no "thrust" label on one side, because there is. They are definitely radial bearings and not angular contact bearings. They are a matched set built to ABEC 3 specs. They are the exact part number that was in the machine spindle before.
Will they work, I have no doubt. The question is how will they perform. I have no way of knowing if the bearings will be properly preloaded for this application.

Scott
 
Last edited:
"Because the bearings are radial, both sides look exactly the same..."

You just told me those bearings will not work in your bridgeport spindle.

Jim

Nothing wrong with radial bearings. BP used radial spindle bearings in the first 1/3 or so of it's heads. Of course you can't just drop in any set of radial bearings. I had read that BP would grind the bearings on a custom basis to set the proper preload.
 
They are bagged separately but boxed together ... at least for this set. Image above has been updated ... much better after the first coffee :)
 
The DB indicates they are for back to back mounting, which can be accomplished either directly or via matched spacers for spindle stiffness. You might want to measure your spacers (prefereably to within 0.0001") to see if they are matched. If so, preload should be set for you.
 
"...BP used radial spindle bearings in the first 1/3 or so of it's heads."

Yes. But did you ever take one of those M heads apart? I did.

Very peculiar construction. The bearings were standard SAE206 radial bearings
but bridgeport custom modified each one. I still have the take-out bearings
so I could shoot pictures if you like.

They custom ground the face of each outer race, to turn the bearings into
a rough approximation of angular contact pairs. The OD and ID spacers
were ground to be exactly the same length on those heads, each pair of
bearings was custom prepared to achieve correct preload in that setup.

A person who attempts to install radial bearings that have not been prepared
in this way will right away find there's a huge amount of slop in the spindle
when assembled.

If they are true angular contact pairs, or have been othewise custom modified to
operate together as such, then it might work.

In my case I purchased two individual ABEC-7 radial bearings, and trimmed the
OD and ID spacers to achieve correct preload. It was a tough job and not worth
it if one can simply purchase the correct angular contact pairs from a reputable
manufacturer.

Jim
 
Good points Jim and I've found that some of the parts sellers (/rebuilders) are quite knowledgable and will confirm the manufacturer and class of the bearings they sell. One guy says his bearings are Barden ABEC-7.

Speaking about not worth it, if one is about to part with $300 for a set of bearings, they might want to go for the $400 deal from Wells Index, that has been mentioned on-line and is offered on Ebay. Send in the spindle and get it back with 3 new bearings (top and 2 ABEC-7 bottoms) and the R8 nose taper re-ground in place for near zero TIR.
 
Sounds like the extra hundred, well spent.

I know that as a novice, it took me many hours of head scratching, and custom
fixture fabrication, to install those abec 7 bearings in that M head. As soon
as you wind up modifying the spacers to set preload, it becomes a real issue,
because you cannot install the bearings on the spindle itself to check the
clearance - because once they are installed, one has to press though the
balls to remove them, to trim the spacers.

Final solution was a custom-made fixture that looked like the quill nose and the
spindle bottom, but which did not require large press force to install or remove
the new bearings. Then I could assemble, check the clearance, trim the
spacers on the surface grinder at work, check again, etc.

Also remember that the measurement for the clearances at this level means you
need a GOOD dial indicator, I was using my federal electronic setup to do this and
I needed it.

Jim
 
Speaking about not worth it, if one is about to part with $300 for a set of bearings, they might want to go for the $400 deal from Wells Index, that has been mentioned on-line and is offered on Ebay. Send in the spindle and get it back with 3 new bearings (top and 2 ABEC-7 bottoms) and the R8 nose taper re-ground in place for near zero TIR.

Is this for a Bridgeport spindle? I wonder if they can do this and regrind the NMBT 30 taper from a Bridgeport BOSS? Dennis
 
I don't think it is mentioned on the site as I looked at it this morning. Here are the ebay links:

Bridgeport (3 bearings replaced): http://cgi.ebay.com/R-8-spindle-gri...m?hash=item120286391871&_trksid=p3286.c0.m234

Their ebay store lists other spindle regrinds (including NMTB40 regrind only):

http://stores.ebay.com/Wells-Index-Milling-Machines

And they include this comment:

quote "Some of the mill spindles we can grind and rebuild include Wells-Index, Index, Bridgeport, Lagun, Clausing, Supermax, Comet, Etc.... Please e-mail your mill model if you are not sure."
 
Rich, Not to confuse this with the OP but my bearing set, same number, also has an Fxxxx (can't get at the number right now) "customization" suffix.

The J prefix is extra loose internal internal fit, the single M is ABEC-3

Polaraligned, I believe the set I have is fully marked and will shoot or scan it tomorrow and post here. That may help you to ID the sides.

Incidentally, without the 2MM prefix, it seems like these are not even angular contact but I'm not sure about that.

OT - I have a BPT bearing headache. Last week, searched on line for bearing numbers for the 1HP BPT original motor and ordered some from MSC. They arrive, I pull it apart, wrong size bearings :eek: Order the right size this time, take the motor apart today, the rear bearing is a different size :eek: I suppose the old adage "hast makes waste" still works. Don't know if I've taught that one to my kids. :)


The M and 2MM are available in both radial and anguar contact types. If the bearing in question were true angular contact type, they would have a W suffix - like 2MM207WI DUL. Dig deep on Fafnir's site, and you find the JM207PRB DUL listed under "aircraft magneto bearings". Call their tech support for detailed info -they are very helpful.

Yes.. there are a couple of different bearing in BP motors.. I have two different configurations...
 








 
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