Thread: Steel hardness

Hello,

I have a fixed blade razor i'm making got it heat treated and tempered. I tempered it straw colored in the oven at 400 degrees C for 2 hours. But it's still harder then my Dovo, Sheffield. And my axe file won't bite into it. Should i retemper?

did you aim at particular HRC? If I am not wrong most razors fall in the 58-61 HRC range, Sheffields may be a bit softer.

For starters telling us what steel you're using would help. Also your heat treat procedure if you did it yourself.

Can't tell you the steel, I made it from a really old file. If i had to guess O1 tool steel. I heated it up to curie point then past a little for a few minutes quenched it in water. Heat treated for 2 hours at 400C.

400 C (750 F) would be much too high a tempering temperature for O-1. It should not skate a file. Most old files are W-1 or the like, that explains why it survived a water quench. The O-1 would have come apart.

Now if you mixed up the thermometer scale and it was 400 Fahrenheit....then try it at 425 F for another hour and retest it for hardness. If not to your liking then, 450 F for another hour. If it is Centigrade temperature, then I think you have a steel that is not behaving like a normal tool steel. Some stainless stuff will have a tempering cycle up to 1000 F but not something usual for a file either.

That's funny sorry i got the temperature scale mixed up.
I don't have an up to date picture. This ones right after hardening. Now it's grind, and shaped and partly polished. but it's still a little wide at the edge, i intended it to be a wedge but i can't hone it yet cause the upper part of the bevel is to thick and i can't get to the edge. It was taking so long on the 1000k i tried the file but it just skipped off. So is it too hard? It can almost scratch glass.

if it can scratch glass then the HRC is 63 or higher.

I think you're off to a good start. Simply increase the temperature by 25 degrees for one hour. If you are patient and take that in steps you'll arrive at a hardness you like that won't abrade your stones.

Working with mystery steel has its challenges. O1, W1, S7 or maybe 1095???? Who knows. I have tried to look up which steels file manufactures use with no luck. Grind, grind, and grind some more. I don't expect that you will get to where you will be able to shape it with a file. When you do get it annealed then it is time to shape then re-harden it. Kind of a hassle to get right, when we don't know the steel. I have a couple of knives made from files. I have another 2 I softened with a torch. I brought one to the non magnetic state and quenched in oil. I had not drawn it back any and I broke it when rockwell testing it. The grain structure was huge. Drawing it back would have helped some but I will have to play with the HT process some more before I HT the 2nd blade.

Rambling, but I recommend grinding to shape then draw back slightly, no water quench. Do not worry to much about whether you can cut it with a file.

Jeff

Two things come to mind Jeff.

The first is that the file was probably overheated at some point if the grain size was large. It is possible with some simple techniques of thermal cycling to reduce the grain structure and salvage these.

Second, there are modern files that are merely mild steel that have been case hardened (very shallow depth of hardening) only meant to have hardened teeth. This saves a good deal on material costs, but often interrupts the blade maker's quest for a file worthy of making/recycling. Stick to Name Brands and preferably the older the better.