my first knife wip: need help with tempering.

[Guest guest T]

I have started making my first knife today and I am done forging. it is made from an unknown steel that was coated in copper. when It eas quenched it became so hard my file barely scratches it and 120 grit sandpaper won't scratch it. what temperature should I temper it(max 550 F) and will it be easier to file after I temper it?

Edited October 2, 2013 by Tre Asay

[Geoff Keyes]

Congrats on your first knife, welcome to the dark side .

 

With unknown steel, you're just going to have to experiment with all aspects of the heat treating. However, you should temper immediately after hardening, you risk stress cracks otherwise. If it's hardened and tempered (and you get a reasonable hardness out of it) you may not be able to file it at all.

 

You've made a mistake in process, one that you can recover from. The steps I follow when making a knife, in order are

 

1. Forge
2. Remove the scale
3. Profile
4. Rough grinding (grinder, file, drawfile, whatever you've got)
5. Harden
6. Temper (right away)
7. Finish grinding
8. Polish
9. Handle and furniture

The scale can be taken off with an angle grinder, or an overnight soak in vinegar and then a wire brush. The scale is harder than steel, so you want to take it off before you start grinding. Profiling can be done with a file, or a bench grinder. Finish grinding is going to be a problem, if you don't have tools, then elbow grease will have to do. You may end up having to use 36-60 grit paper and a block. Polish is up to you, I like the black automotive papers and I often go up to 1200-1500 grit.

 

If I were you (and I'm not) I would call this one a lesson learned and start over. If you choose to proceed, take a mid red heat on it and let it air cool to black a couple of times, then go up to the list and start at step 2. Also, do a search here for "Normalizing".

 

Good luck,

 

Geoff

[Guest guest T]

thanks, I tempered it at 470 for 1 hour 15 minutes and I am just going to try to grind it with my file after it cools. I have 120, 220, 400, 1000, 1500, and 2000 grit sandpaper so I will tell you how it works when(if) I can sharpen it.

the edge is already fairly thin(about 5/64 in) from forging and it is not super hard so I think I will be able to grind the bevel and sharpen it.

Edited October 2, 2013 by Tre Asay

[Caleb Harris]

Also, just after forging one is supposed to normalize; heat to critical, then let it cool 'till it's black. This minimizes grain size and reduces stress.

[Guest guest T]

I just finished it and it is a bit of a mystery to me. it was easy to file after tempering and seemed soft but once it was sharp I was able to cut hardwood against the grain without the grind bending or dulling.. any ideas on what it might be? I did not normalize but the blade was thin enough when I was almost done that it cooled from orange to black in seconds.

 

 

 

 

 

 

 

[JoeReese]

Geoff, I just tried to "like" your response, but I'm too new to have that ability.

I have not spent much time here, but my experience elsewhere on the internet usually

includes people jumping all over someone's mistakes and not answering their initial

question after all. You, on the other hand, took the time to try to actually help the

original poster. It's one of the things I like a lot about this forum so far, that one

rarely sees elsewhere on the net. I think your advice will also help me, once I am

ready to try forging. Thank you.

[Geoff Keyes]

Thank you for your comment. Our founder, Don Fogg, tried very hard to foster an environment of polite and helpful discourse. As a fairly senior member of this community I try to live up to that ideal. I'm pleased that you noticed, and I'm pleased (and just a little sad) that you think my response was worthy of comment.

 

We have all started somewhere, and often our first efforts are kind of crude. You should thank your lucky stars that I have managed to hide most of my early efforts.

 

Thanks again,

 

Geoff

[JoeReese]

You're welcome, Geoff. I try to call it as I see it.

[Doug Lester]

I think that you will find that a lot of knifesmiths have done away with annealing after forging. Normalization will make steel just about as soft as you need and a critical anneal can cause problems with carbide growth. There is a process call sub-critical annealing but, seeing that you're a beginner, let's not get into that. It seems to be more important with higher alloy steels that smiths don't work with much. Geoff covered the process real well.

 

Doug