Hardening chisels

[John C Cox]

Heres the basic process and junk needed to harden and temper chisels.
Note: do this at your own risk. You will wreck some chisels. And you might catch yourself on fire... Don't say I didn't warn you.


The Stuff.
Oxy-mapp gas torch
file
magnet
cup full of olive oil (canola, soybean, and peanut oil also work well).
Fire extinguisher
gloves
vice grip

https://s15.postimg.org/h33de7wvf/image.jpg (https://postimg.org/image/d6q1i8bvr/)

The flame

https://s15.postimg.org/3ngcorodn/image.jpg (https://postimg.org/image/sthavlpnr/)

What it looks like with no flash in the dark when the magnet no longer sticks.
I would call this orange, but I am going by the magnet.

https://s15.postimg.org/41hood8h7/image.jpg (https://postimg.org/image/hv61df12f/)

With flash - same as above but brightly lit. Nonmagnetic
https://s15.postimg.org/551t0bt4b/image.jpg (https://postimg.org/image/gu5soak2v/)


Quench in oil. Up down up down.
Don't stir around or it may warp sideways.
test with a file - the file should skate on the hard end now.

Note: this is a cheap Harbor Freight chisel and wouldnt harden in oil....
See next pic for what happened when I hardened it in water...

https://s15.postimg.org/q37yyesyz/image.jpg (https://postimg.org/image/ee3zag207/)

This one was water quenched. Crackity crack. Wouldn't harden in oil.... .

https://s15.postimg.org/syl259wyz/image.jpg (https://postimg.org/image/tbcgbgf8n/)

Dont say I didn't warn you about warping.
Don't be greedy - only harden the first 1".

https://s15.postimg.org/flcv5jlt7/image.jpg (https://postimg.org/image/4yj204dnr/)


Temper in 400F oil for an hour or 2... I don't like chippy edges.

https://s15.postimg.org/uu7ugflt7/image.jpg (https://postimg.org/image/kk5fh6vxj/)

Next - re-establish a nice flat back and then sharpen.

These are much harder than straight out of the store...

[James Pallas]

Interesting and straightforward post John.
Thanks
Jim

[John C Cox]

Here's the chisel - untreated and after quench and temper.

https://s12.postimg.org/p4sc0go65/image.jpg (https://postimg.org/image/qjtwp6p95/)

The Buck Brothers chisel behaved beautifully. And they are available at the Local Home Depot.

Also oil hardens successfully:
Irwin/Maprles blue chip
Footprint 87 series blue handle

Would not oil harden:
Narex - water hardens well but warps.
A miscellaneous no-name German chisel - water hardens well but warps
Harbor freight wood chisels - cracks on quench in water. Temper goes soft at a fairly low temperature. Behaves as if it's some sort of low/medium carbon alloy...