Grinding removes temper?

**ryanarcher** · 12th May 2004, 05:24 PM

Does anyone know at what tempreture tool steel loses it's temper, and how long you can sharpen on a typical bench grinder before this happens? I'm fanatical about the edge on my woodworking tools and have a water cooled tormek system that works great. However, I'm trying to get the guys at the firehouse to sharpen the axes and other firefighting tools by hand instead of grinding them. Some people say that the steel does not become brittle until it discolors, and others say that the extreme edge loses it's temper imediately upon contact with the grinder. Anyone have the facts? Thanks in advance. Have a good one, guys.
-ry

**ozwinner** · 12th May 2004, 06:29 PM

Hi
Carbon steel doesnt change its properties until the steel glows cheery red, approx 850c.
High speed steel (HSS) will still cut even when glowing red, I would have thought that tool steel would be even better than HSS.

Cheers, Al

**echnidna** · 12th May 2004, 06:40 PM

Back in the olden days I was taught that the steel loses its temper as soon as it starts to change colour.

**ozwinner** · 12th May 2004, 07:47 PM

Some years ago ( 12 ) I did a 3 year welding course in Ballarat, and thats what we were told.

Cheers, Al

**Jim Carroll** · 12th May 2004, 11:01 PM

The redder I get the temperer I get :mad:

**morry** · 13th May 2004, 12:14 AM

The way I understand it Carbon tool steel needs to be heated to dull red heat (no longer magnetic) then quenched quickly in oil or water to bring it to maximum hardness. The Steel is then polished and re heated until the various temper colours are seen on the polished steel. Straw colour is a good balance of hardness and ductility and hardness goes down as you reach purple then blue. HSS needs to be taken to almost white heat to retemper.

If you grind any tool steel and keep it cool by dunking it into water often so no colour change is seen you should not loose any hardness.

**soundman** · 13th May 2004, 01:19 AM

Firts you need to establish what sort of steel you are talking about.

I wouldn't expect an axe would be much more than one of the lower high carbon steels.

secondly how much does it matter, a firemans axe isn't a fine edge tool by any means.

I wouldn't expect to actualy cut anything with a firemans axe more bludgeon it into submission, being vaguely pointy is probably OK.

The other abuse the axe would be subjected to probably makes sharpening method pretty unimportant.

I mill file gets my axe plenty sharp for garden chopping.

cheers

**goodwoody** · 13th May 2004, 01:52 AM

An axe should be filed and then stoned, not ground.
I was taught by a Queensland axeman.

**ryanarcher** · 13th May 2004, 02:14 AM

Thanks for alll the help guys, I'm much appreciative. It's great having such a wealth of info my fingertips.

soundman,
secondly how much does it matter, a firemans axe isn't a fine edge tool by any means.

I wouldn't expect to actualy cut anything with a firemans axe more bludgeon it into submission, being vaguely pointy is probably OK

You'ld be surprised, for some forcible entry applications, you have to be able to shave with the tool. You are right though, I need to find out exactly what kind of steel it is.

Al, Goodwoody,
Thanks for sharing your great info.

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