Hardening metal

[I like karts]

I think if you heat metal red hot, then dunk it in used motor oil that is dino and not synthetic it hardens it. It bonds more carbon to it, therefore making it harder. Be careful though, cause it makes a lil fire. (Saw them do it on mythbusters)

 

[ryf]

the used dino oil is the most correct way, the thing you need to do is put it into the liquid and swirl it around, you can't do that as safely with oil, water works, used dino oil works better as it does allow carbon to bond as well, the other reason people prefer oil is you can reheat repeat and add more carbon, I have made knives this way. another thing to think about, is keep your old lawn mower blades, and if you need something already tempered, its thick, strong and tempered.

remember you must swirl it to temper properly, the boiling of the liquid along the surface slows the temper, and you want this to be cooled as quickly as possible (I've gone so far as to swirl in ice water with good results. if you just drop it in the oil or water, it will temper, but not nearly as well. have fun with it.

 

[MDMike]

first Id heat cherry red, quench in oil, Then heat cherry red and quench in water. There's several ways to harden steel. Casolite (case hardening) which is a powder used after heating red hot.
But the oil and water works well. (I come from a Machinist family)

ps. Yes be careful of fire when using the oil.