Thread: How hot to retemper steel?

Questions always lead to more questions. kevint is hinting at the correct process.

I think you are asking about re-hardening the blade. If that's the case, you'll need at least 800C or 1500 F for a carbon steel and probably higher for stainless.

Re-hardening the blade can be done, but not in home build shop equipment and even then, with a finished-down-to-sharp-razor-blade there is a strong possibility of creating a newly hardened blade with a wavy potato chip edge.

I still need to know more about this blade. Where in MN? Send me a PM please.

You will need a forge and heat treating furnace/oven; it can be done with a torch but the results won't be as consistent as the two former. You could always send it over to a bladesmith but he will still guess work... to know exactly what kind of steel used in the razor you'd need access to a laboratory and a good chunk of that steel or there's always the grinding sparkles' test but I don't think you wanna do that! :P


To answer the question... the temperature should be just above non-magnetic range, most probably around 1400-1500F. But the razor WILL warp and be unusable, no questions about it. I'd just continue to use it like it is... does it shave well still?

Else, in the event that you get a forge, you could still use it to make some pattern welded blades.

Here's a good link about temp ranges:

[ABANA] Tempil Guide

It is not possible, if you dont have a wedge. With a halfhollow or hollow razor the result will look like this:


This razor I grounded to thin before the hardening Before the hardening you need at min. 0,5 mm thickness at the edge.

May I suggest that before you go the heat treating/tempering route that you should first verify that the blade has lost its temper ( it is to soft). Just hone up the blade and see if it will hold an edge thru a number of shaves. One of the indicators of softness that you can check for is microchipping on the edge while honing. If the temper has been lost then( steel is soft) it will not be strong enough to hold an edge when the steel is very fine/thin, i.e. 8000 grit.

Mike Blue is a very good and competent person to talk to regarding heat treating/tempering of steel.

Hope this helps,

Originally Posted by HNSB

How would a person know what type of steel the razor is made out of?

They wouldn't. Seriously.

Originally Posted by HNSB

Maybe this is something that is just not possible for the amateur?

Indeed.
Also note that razors are ground after heat treatment because the blade needs to be solid enough to survive the thermal stresses of rapid cooling (among other things).
A hollow ground razor will not survive this.

i ll have to get a pic of what razors look like in my shop before heat treat

i can tell you this cause of the soak times in my kiln i only part grind and leave the edge around a nickle thick
if there is any warp at all i can grind it out
and remember there is less good steel after heat treat cause of decarb (less you run salt pots) so leaving a bit to grind away is a good plan

yes its a bit harder on belts and takes a bit longer over all to grind but at least you get a finished blade