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audrey
08-15-2003, 02:11 PM
Hello I am repairing a shaft end. I turned the damaged end down and made a A-2 bushing to press onto it. The bushing is still Oversized .020 in Diameter. After Heat Treating I will press it onto the shaft and turn it down to the finish diameter. The problem is that it fits into a roller bearing. How hard should the bushing be and how do I get like a super fine finish on the bearing surface? Do I have to grind it? Thanx Audrey.

Evan
08-15-2003, 02:27 PM
Have a look at this:

http://www.maintenanceresources.com/ReferenceLibrary/Bearings/rbshf.htm

If I understand correctly the shaft is the inner race of the bearing. In that case you will need a microinch finish on the order of ten microinch. It should be hardened to RC60 or so. To obtain the required finish you can grind or you can single point turn and then use a roller burnisher. To obtain the required hardness you can case harden with Kasenit or Quick-Hard. Apply three times to hit RC60.

I just looked up the properties of A2. Never mind the case hardening, not necessary with A2. It will air harden to RC60.

[This message has been edited by Evan (edited 08-15-2003).]

wierdscience
08-15-2003, 08:41 PM
Just a dumb question but you couldn't use a off the shelf needle bearing inner ring instead?

Thrud
08-16-2003, 02:21 AM
audrey:
Unless you are willing to go out and buy a CBN insert to hard-turn that hardened A-2 bushing - forget it. It will have to be ground.

Hard-turning with CBN will give a finish as good or better than normal grinding.

I would presume you are talking about a normal ball beariing and not a roller bearing that requires a hardened shaft to ride on. If so, no special surface finish is required, but it does not hurt to use some loctite (bearing mount) on both the shaft and housing to prevent turing of either in service. A roller bearing requires a hardened & ground finish (or hard turned) on metal normally.

Evan
08-16-2003, 04:04 AM
Thrud,

You gotta stop skimming. She said roller bearing. The shaft is the bearing surface.

Audrey, if you will grind it you can do so after the final heat treatment. If you are going to roller burnish it ( not a commonly held tool) do so before final air hardening. I like Wierds idea of finding a fittable inner race, if it is not too late.