The Home Machinist!

Just got my tool post grinder set up and now I'm trying to grind a axel shaft to fit a closed needle bearing. The size of the bearing ID is suppose to be 9/16. I've called a couple of bearing places and they say the shaft size should be .5631 to .5635 for this bearing, however when I grind it down to .5631 the bearing will not fit, not untill I get down to .5610 does the bearing begin to slide on and it's real sticky(kinda ratchets when you turn it). When I get down to .5600 the bearing fits smoothly but when you turn it the needles tilt in the cup and the bearing tries to screw itself in one direction or the other depending on the tilt. The finish on the axel is very smooth. My question is what should a bearing fit look like or feel like when you have the right tolerences.

Are you using an expander on the end of the shaft to spread the rollers? Without an inner race, you need to expand the rollers to their full opening size so that they will fit over the shaft, otherwise they tend to hang up on the shaft end, giving you the impression that the shaft is too large.

Mike

Mike

No expander, never heard of that. Is it something I can make ?

You don't say if this is a drawn cup needle bearing unmounted, or a needle bearing with an outer race. ?
A drawn cup bearing is in a thin steel cup and should NOT be used for fits evaulation as it is unmounted. Normally the cup is "pressed" into a housing or support, which will shrink it's size by .0005 or so.
For your info, a cup bearing w/ 9/16 bore, say a B-96
(B is series/load, 9 means 9/16 bore,6 means 6/16 wide(3/8))
needs the following for a standard precision mounting:
Shaft size .5620 to 5625
Housing bore .7495 to .7505
If you bought a factory inner race to run on this bushing , ie.IR-68, it would have a diameter of .5625 (+.0000 / -.0005), so I don't understand what other folks are telling you.
The other post mentions a pre -shaft of sorts, that is you use it to get your bearing started straight ,which is a good idea, but when the bearing "screws" on to the shaft, the fit is too tight and the needles can't correct .
When mounting a Drawn cup bearing in a housing, you should make a temp stub shaft (small size)plus have a shoulder to push the cup into the housing squarely !
Good Luck

What I'm trying to do, is replace an oillite type of bearing with a roller type since the oillite bearings fail rather quickly and other types of brass bearings we have tried fail just as fast. The oillite size is 3/4 od and 1/2 id and it takes two since the crank shaft is 6in long and is supported on both ends, pully on one and the crank on the other. The closest size of needle bearing I can find is a B-912 since I can change the shaft size(.5 or larger) but not bearing od (I'm stuck with the .7480). I was told you could use drill blanks as axels by grinding them to the final tollerance. I forgot to mention that I was using a piece of stainless for the test axel, so maybe that was causing the stickyness. It's a draw cup type of bearing.

Your axle needs to be hardened to 56+ RC or the needles will
enbed into the the new axle. Info from Torrington Reference book.

Also, lesson bought and paid for by experence.

I'll echo Rich's suggestion about using a driver. I'll also go one further and suggest that the driver surface that contacts the bearing is angled such that the contact is toward the ouside (closer to the housing) so that it will be less likely to bend the outter edge of the bearing housing. It's been a while but I believe we took this right out of a Torrington catalog as well. We likely looked into it because of premature failures. When we used them they always felt smooth as silk when installed correctly.

To ech another thought (about proper hardness) not only should the surface be hard but the amount of hardness (depth of hardness) is critical as well - again this too was learned the HARD way. Too shallow a hardness may result in flaking.
With all that said you might also conside rcheckign into some of the composite type bearings - we have had VERY GOOD LUCK with IGUS brand bearings . they have LOTS of applications and wear amazing well - one Pro is that you can run these on softer shafts only Con here is that they DO NOT perform nearly as well on SMOOTH shafts - they are designed to run on rougher shafts - GREAT FOR REPLACEMENTS were a drawn cup bearing might have damaged your shaft.

Just a thought (or two)