304 Stainless Ball Bearings

[RJSakowski]

Is it possible the bearings are case hardened? With a process known as Kolsterizing (carbon diffusion process), surface hardness's of up to 72 RC on austenitic stainless can be achieved.

 

[rgray]

Is it possible the bearings are case hardened? With a process known as Kolsterizing (carbon diffusion process), surface hardness's of up to 72 RC on austenitic stainless can be achieved.

I about said that earlier. My thought was grind a flat spot and then see if it can be drilled.

 

[RJSakowski]

I about said that earlier. My thought was grind a flat spot and then see if it can be drilled.

From what I read, the process creates a shallow case (22 -33 microns). so grinding the flat could very well work.

 

[RJSakowski]

I missed the part about being magnetic. Based on that property, I would suspect a martensitic 400 series stainless.

From Crucible Industries, to anneal 440C, heat to 1650ºF, hold for 2 hrs. and cool slowly (<25ºF/hr) to 1200ºF, then air cool. At that rate, you can expect the initial cooling to take 18 hours.

To achieve this without a furnace, I would heat a pail of wood ash to the annealing temperature and place the bearing in the center to cool. Not perfect, but it may do the job.

 

[rwm]

I was able to drill into this about 2mm with a solid carbide bit but it was like drilling tool steel. It was going to destroy the drill so I stopped. There is no way I could tap it. Seems to be hard inside and not just case hardened.
I am abandoning these balls in favor of machining my own or buying from MMC!
R