View Full Version : Need to make a hardened bearing cup

1937 Chief
02-01-2010, 01:32 AM
I am restoring a old corbin motorcycle speedoneter. There is a very small bearing cup probably 3/8 id .040 wall X 1/4 thick. It has a row of small bearings around the center held in by grease, and a hardeded tapered shaft is centered in the berarings. The smal bearing cup is rust pitted. What would be the best material to use to make a new part, that I can harden in my shop, and how to go about it. I cleaned up the hardened tapered shaft with my tool post grinder, it turned out real good. Thanks stan

02-01-2010, 06:08 AM
Hmm. I did something like that long ago. Got any 1/2 inch or 5/8 inch steel balls laying around? A ball from a cv joint would do probably. I heated one up and let it cool slowly, then put it in the 3 jaw and turned a bit of a post on it. Turned it around, turned the outside, remounted it on the larger diameter, then drilled and bored it. After that it was steel wool jammed onto a stick, which I worked around as the lathe was spinning. Then Nevr-dull, same thing- jam it in the hole and work it around, expose new wadding as it got blackened. Cleaned it up, heated it cherry red and dunked in oil. Steel wool and Nevr-dull again, then called it good. It had five balls in it, with a tapered shaft like you spoke of- sort of a combination thrust and radial bearing from a weigh scale.

02-01-2010, 11:09 AM
Couldn't you just machine one out of some tool steel and cut the inner race with radiused cutter in the compound and then harden it?

That is, I am assuming there is a radius in the race for the balls to ride in and the tapered shaft holds them in. Is that so?

1937 Chief
02-01-2010, 01:01 PM
I can make the part ok, but Ineed to know what steel to use, and how to harden it. stan

02-01-2010, 01:51 PM
This is not the profeshional way of doing this but it will work just fine for what you are doing.
Use A-2 heat it red. As soon as it turns red drop it in water. When you do this it will be very hard "too hard" next place it in your oven at 450-500F for about an hour. This will draw it back so it want be too hard.

You can also use 4140 with oil rather then water.

As I said this will work OK for the hobby machinist but it is not the proper way.
I wouldn't want some apprentice tool & die maker to see this and try it at work and get into trouble.

02-01-2010, 06:46 PM
I'd use a piece of water hardening drill rod. Its relatively cheap, hardening and drawing it is decidedly low tech.