HOW TO HARDEN YOUR CHISELS!!! (Full Version)

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HemeolaMan -> HOW TO HARDEN YOUR CHISELS!!! (Feb. 22 2008 13:33:28)

k guys, i did a little looking around

an old school method for hardening steel and increasing carbon content:

heat up the metal til its red hot, then quench it in USED motor oil. used oil has a great deal of carbon which is absorbed by the metal as it cools.

always do this outdoors where nothing can catch fire

this will make your chisels incredibly hard. they will retain an edge longer. at a cost they will be marginally more brittle.




guitarbuddha -> RE: HOW TO HARDEN YOUR CHISELS!!! (Feb. 22 2008 13:37:06)

How about continuing to use a blunt chisel and claiming it is sharp ? Then you could claim that any method for sharpening chisels is pointles and complicated.

I believe that people who feel the need to sharpen their chisles dont really 'feel the wood'.... or do I ?

[:D]




Martin -> RE: HOW TO HARDEN YOUR CHISELS!!! (Feb. 23 2008 4:57:57)

The exact shade of red matters, think cherry.
Used to do it with coal dust as a case hardening medium a few times followed by a quench.




JBASHORUN -> [Deleted] (Feb. 23 2008 7:29:07)

Post has been moved to the Recycle Bin at Apr. 11 2011 17:42:57




Shroomy726 -> RE: HOW TO HARDEN YOUR CHISELS!!! (Feb. 23 2008 10:56:40)

Well, as a mechanical engineer I gotta make a comment [8D]

The hardening of carbon steel highly depends on the temperature at which the metal is heated and at what rate the metal is cooled. If you do what you say you wouldn't really be increasing the carbon content of the "whole" piece, but rather just the exterior surface. It would have a sort of "carbon" case which is only good for the sharp part of the chisel. Depending on the carbon content present before quenching, the chisel will remain in different phases. The phase you are talking about, when you quench it in a relatively cold fluid (I wouldn't advice motor oil because it gives off fumes and smoke that are bad for you) to room temperature it's called Martensite, a non-equilibrium single phase structure that results from a diffusionless athermal transformation of Austenite.

So the faster you cool the harder it gets, but as you said make sure the metal is red hot. You can "reset" the metal's previous heat treatment by reheating it to around 750 C. After quenching it in quenching oill which is designed for a high flash point and quick cooling to ensure thorough hardening (cooking oil is another choice, but won't get as hard), I would temper the tip where the hammer hits the metal so that it is a bit soft by leaving it unquenched. The ideal would be to heat the impact tip to about 280 C and letting it cool to room temp. That's how you temper it. So then you'll have a sharp chisel with a non-brittle impact zone.

Annealing is called when you cool the metal very slowly, in order to reduce the hardness and allow you to cut and shape the metal.

And yes, I'm a nerd. [:)]




TANúñez -> RE: HOW TO HARDEN YOUR CHISELS!!! (Feb. 23 2008 14:08:35)

quote:

The hardening of carbon steel highly depends on the temperature at which the metal is heated and at what rate the metal is cooled. If you do what you say you wouldn't really be increasing the carbon content of the "whole" piece, but rather just the exterior surface. It would have a sort of "carbon" case which is only good for the sharp part of the chisel. Depending on the carbon content present before quenching, the chisel will remain in different phases. The phase you are talking about, when you quench it in a relatively cold fluid (I wouldn't advice motor oil because it gives off fumes and smoke that are bad for you) to room temperature it's called Martensite, a non-equilibrium single phase structure that results from a diffusionless athermal transformation of Austenite.


I was just about the say this. [:D]

Seriously though, is hardening your chisels even necessary? My chisels are hard enough. Never had a problem with them being too soft or maintaining a sharp edge. As long as you buy good quality chisels and keep them maintained, I don't see the need to have to harden them. If it'll keep an edge and cut, I could care less what the carbon content is. Save the steel hardening for the Samurai sword makers [:D]




Shroomy726 -> RE: HOW TO HARDEN YOUR CHISELS!!! (Feb. 23 2008 15:25:11)

I've never had a problem with a chisel before, but if it's like you say and buy one that's bad quality you might need to harden it.

Talking about Samurai swords, the Japanese do this quenching process but do it with piece of metal that has been folded along its longitudinal axis several times. It's still made of martensite steel with a mix of a softer steel phase. Pretty cool eh?




HemeolaMan -> RE: HOW TO HARDEN YOUR CHISELS!!! (Feb. 23 2008 16:34:21)

okay.




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