Hardening a Mild Steel for use as Bearing Surface

You can successfully harden steel the way you are thinking but I think the driveshaft is only a machined surface the race of the bearing or inside diameter should move with the shaft .It may have siezed and looked as though it should have been hard check out the new bearing or replace it with a bearing with a race .

you can't harden mild steel as the carbon content is to low for a martensitic grain structure to be formed during the heat treatment process.

If you really need a hardened area for the bearing better to try and find someone who can case harden that area for you, not a very difficult process if you are not too concerned about thickness of hardened skin and shall we say "quality control"

The short answer is NO. Mild steel can be case hardened but not through hardened. The rest of the processes you describe will kill your axle through heat, stress and alloy dilution.

Hi, I understand about trying to make things work when you don't have access to the right stuff. Regarding rebuilding a shaft for antifriction brearings to run against, it is almost impossible to do a quality job. If you are able to carburize (case harden) the shaft the case will be too thin/weak compared to a proper inner race. That doesn't mean it won't work, but that it will make the original engineer wince! Other repliers to your post assume the shaft is mile steel, but that may not be the case. I suggest that you try to find out what it is made of, being a drive shaft it might be of better quality and able to be nitrided. If this is the situation then maybe you can get a harder surface that way. It still won't be what a text book defines as a proper surface for the application but it might be worth a shot??? Otherwise, see what antifriction bearings you can lay your hands on and use them, even if they are undercapacity, they will be a better bet than running a ball/roller bearing on a rebuilt low grade shaft. Good luck!!! ps if you want to take this offline my email is ericssonkarl@netscape.net , I am more than happy to help out if I can.

Usually, the complete bearing -[inner race with bearings and outer race]is pressed onto the axle. As bearings fail, metal melting temperatures cause bearings to crumble. Enormous rotating forces often jam and lock the crumblinng bearings to the inner & outter race. Melting hot. A slight heat expansion of the pressed-on inner race permits it to now slip on the axle surface. More destruction quickly occurs. The results look like what you see. File/grind this metal migration off and press on a new bearing - USA bearing price, under $50.

It's interesting several people offered advise on an axle although the subject was a driveshaft .The fact remains even if it where, is to get a result , he might try an old trick .To pin punch the surface to puff it up to hold the inner race if that applies .Otherwise the original Idea of hardface welding and machining is still a good approuch as the new materials have the hardness for the job .Best of luck Driveshaft Man