Bearing replacement on vertical mill Y-axis

I have one of the fairly rare, and none too sophisticated Jackson vertical milling machines. Think 2/3 size Bridgeport, with 3hp and a B&S10 taper.

To the point - trying to tighten up the machine some, the y-axis lead screw has a single 6202 bearing at the crank end to take the axial load in both directions. Best I can figure, is that about 0.010 of y-axis backlash is due to this bearing (measuring end play of the leadscrew). Outer race is tight to the frame, inner race is tight to the leadscrew.

Bearing data - SKF HC LO2 I 70747 HC

etched on the edge of the inner race is 6202
both sides open
35mm OD, 11mm thick, 15mm ID (measured with a scale)
Oil hole to feed the bearing occasionally
Bearing runs smooth, but obvious side to side movement of the inner race relative to the outer race.

So this one bearing takes the axial load in both directions as cranking the y-axis in and out, as well as a little radial load. Is this the best bearing for the job, or there another one the same size that is better for axial loads? No other simple way to get another bearing configuration in the space.

Any help appreciated.

I'd just get another bearing same as that one, mill must be at least 50 years old? I can't imagine any reason to re engineer it now; if you have trouble finding one with an oil hole in it just get one and pack some grease in it.
Dan

The thing is, I don't know one bearing from the next by sight or even number. Some ham-fisted hammer wielder has been in there before, judging by the distortion of the pin spanner holes, and vise grip tracks (luckily nothing critical, just a severe lack of finesse).
I suspect the bearing was replaced before, and very possibly replaced with 'one that fits'. It could be the worse possible version of one that fits, but has no axial capabilities. Maybe it is the right one. I am hoping that someone who knows bearings can look at the numbers and application, and quickly say what would work.

Do you have an assembly drawing or parts manual you can scan and ad it here. Does the lead screw and nut have backlash? If you remove the feed dial can you see the bearing move?

You could replace the bearing with a new one and check if the bearing is moving or there is backlash in nut and lead screw. A Bridgeport has a bearing flange with a little lip that pushes on the outer race so it stays put. If the holes is worn out of round have you checked it with a telescope gage? How bad is it. Loc-tite has products you can use to fill in out of round holes.

Page 4-23 , 24 Item 7 - "ring bearinghttp://www.hardingeus.com/usr/pdf/Knee%20Mills/SeiresIPartList.pdf


I found these: I hope it's ok to put this other forum on here...

http://www.alloyavenue.com/vb/showthread.php?6930-Another-Vertical-Mill-thread-)

I have never seen any documentation on the mill, or even heard of a rumor that someone ever had a copy. Design is real simple though. Outer race is captured in a mounting block with an adjustable ring. No way the outer race is moving (I have checked, it is in there tight). Inner race is captured between a step on the leadscrew and a nut tightened against it, again that is not moving.
I am sure there is some backlash in the leadscrew, but since I can measure about 0.010" of movement of the leadscrew when going between turning the crank in and out, the better part of the total backlash is bearing movement. I can see the nut on the shaft moving in and out. When I pulled the bearing out, I can measure about the same amount of play in lateral movement of the inner race to outer.

Just ordered a new bearing, see how that helps.

I see a 6202 is just a deep groove ball bearing, is there supposed to be only one? Usually there's two preloaded against eachother using shims on the inner or outer race. Bridgeports use a better (but pricier) angular contact setup, loaded the same way. I would suspect a new bearing will tighten it up but I'm not sure how long that could last as even a deep groove ball bearing is designed for only marginal thrust forces, and then any wear that occurs translates immediately into end play without an opposing bearing. I'm not familiar with that brand of mill is it somewhat of a hobby grade?

Just one bearing, no easy way to add a second. The x-axis has two taper bearings that can be adjusted.
That is the heart of my question - one deep groove bearing seems not to be the best solution, but perhaps that is what they did due to costs back then. If there is some sort of 'double angular contact in one shell' that is a better solution, but fits in the same space, that would be better. Don't think it exists, but I don't know bearings.
Not a home shop type machine. 1940's to 1950's, 4" quill, B&S10 taper, 3hp, small footprint (8x32 table), and built to a price level, but rigid. Kind of an odd combination of small table and large taper. For the space I have and work I do, it works well. Can easily put a 10" rotary table on it, for what that is worth. Good amount of z travel as well.

If I recall correctly, some bridgeports used a fafnir bearing with one outer race and two inner races, essentially a conjoined pair or angular contacts that took up less space. I would not know the number off hand but maybe someone here does. Maybe a new deep groove bearing will be ok for a decent time, I would think it might be a bit "spongy" with positioning under heavy loads but that's just a guess. I'd have to see pictures of the setup but I would be persuing a modification to somehow sneak another bearing in if it were me, might be easier said than done.

Did you look at the machine Chris? Looks like it would be a miracle if it held .002". I suspect the bearing that is in there was original and if the builder. Plus the screw and nut must have some wear and I bet that would be more of a problem then the bearing. It's nice to see you back! Rich

Just saw the pics, looks like a hobby sized machine but can't really tell the build quality unless I see it in person. I would think one could modify the machine to hold some decent tolerances if he wanted. Good to be back thanks Rich.

From that Bridgeport scan (I didn't see that before), the general arrangement is the same as the Jackson more or less, but that bearings looks to be what I am after, rather than just a single deep groove. I might have enough room on the leadscrew to fit that in, and then just make a new housing.