Bridgeport x/y bearings

[tcweb]

Good day, I need some advice. I have taken apart my 1955 round ram table and saddle to clean out the grease put there by previous owners. What a mess.
While apart, I am curious if I may need to replace the bearings.

The left side of the table, there are two Norma bearings that are 20mm x 47mm x 15.3mm. (not standard 14mm width!) They are shielded on one side only - the two open sides were facing each other. They don't seem to be overly smooth, but after cleaning out some junk, and blowing them out with compressed air, they spin fine, just not "frictionless". Not sure these types of bearings were supposed to spin effortlessly though.

So questions - how do I know if they are OK? They don't seem to have any slop side to side or up and down. I assume these are mainly for the axial load when moving the table (so they may be deep groove bearings?)

Nobody makes direct replacements from what I've learned, so should I put some fresh grease in them and re-use? Or perhaps buy some 6204ZZ bearings and make a spacer for the, so that the overall width matches the originals?

Do I need to worry about the ABEC rating for these, or since they are not for a SPINDLE (just a table), is it not really that critical?

Any advice is welcomed. On a car, it was always easy to know when bearings are shot. Not so easy on a 60 year old Bridgeport, though. (or I just don't know what to check...)

-Tom

 

[JimDawson]

Angular contact bearings perhaps?

They control the axial lash in the leadscrew so deep groove bearings might not be the best.

 

[Winegrower]

I recommend asking H&W this question.

 

[FOMOGO]

Good advice above. From your description I would inclined to reuse them. More important to concentrate on the nuts and lead screws for accuracy. Mike

 

[Ischgl99]

Deep groove ball bearings can be used for axial load conditions, but they are limited to 50% of the radial load rating. Axial clearance is going to be 5x or so of the radial clearance, so if you purchase a tighter clearance bearing, you would get a lower axial clearance. C3 is a common clearance, but that is a step larger than normal, and C2 would be less than normal clearance. You can also get DGBBs in a duplex grind without axial clearance, but those are special order and you might as well go with angular contact bearings at that point. If you put the spacer between the bearing outer rings and can make one accurate enough for the inner ring, you could take up the clearance and make the DGBBs into a suitable solution with minimal backlash.

Angular contact bearings would be the best choice, you can get them with seals on one side and then all you would need to do is make your spacer. Too bad someone didn’t make a wide bearing of 16mm, then you would just need to modify your clamping plate a bit to get them to fit.

This is another option, a 30204 tapered roller bearing is 15.25mm wide and might work. I’m not aware of any sealed versions of TRBs, so you would need to find a way to seal the shaft with this option, but that might be close enough that you don’t need to make a spacer or modify anything else.