First Heat Treatment

[SharpEdge0913]

I am working on my first knife and did my first heat treatment on a test blade (one of the blades I messed up and decided to start over). It seemed to go well, but that could be my lack of experience talking. I am using O1 3/32" flat stock that I purchased from Jantz.

My questions are around determining the hardness from my heat treatment. Basically, did it work. I used an EvenHeat at 1475, soaked for 20 minutes, quenched in warm oil, then tempered 2 times - both at 450 for 2 hours. I dont have access to a rockwell hardness tester, and wonder what other methods there are to determine hardness. I did take a file to it after the quench to see if it skated off... which it seemed like it did. Didnt want to bite into it. But ow that it is tempered, I am not sure what to do.

1) Do you know the rockwell hardness of O1 when in the annealed state? The O1 I got from jantz is annealed, and my only steel experience at this point. If I knew that it might give me a comparison on hardness from hacksawing it. I read somewhere it could be around 35.

2) I was thing of just dropping it on the concrete a few times to see if it breaks. I guess it it breaks then maybe it was too hard right?

3) I was also thinking about putting it in a vise and just trying to bend it up and do the same to some annealed steel to compare. Would this tell me anything?

4) Maybe how the file bites into it as compared to annealed O1?

I am very new to working with tools, steel, etc. I was the kid playing on the the computer instead of in the garage. And continued that into my career. But I love knives. So, I have been reading about knife making for awhile now, and been working on my first knife for several months. Learned most things so far from this site! So thanks for that!

[Ray Rogers]

1) The hardness of steel in rhe annealed state is usually measured on the Brinell scale rather than the Rockwell scale. A Rockwell C scale measurement of annealed O1 probably would not be useful unless you first re-calibrated the tester to some very low range. This would likely mean using the Rockwell A or B scale and even then a comparison wouldn't really tell you much. So, there is no useful comparison between hardened O1 and annealed O1.

2) Yes, if it breaks it is too hard but it wouldn't be likely to break that way since you already tempered the steel. Your heat treating formula seems basically sound, you should be OK.

3) No, it wouldn't (see #1). However, if you found it to be extremely difficult to bend - impossible by hand alone - then that's a good indicator for your HT.

4) No again, same reason. If the file skates off after the quench and before the temper then the blade is probably properly hardened. After tempering tells you nothing unless you happen to be using s special set of files designed to estimate Rockwell hardness.

Don't fixate on hardness, that's just one part of the whole deal. Try the file on the untempered blade and see if it skates, finish a blade and then break it (use a cheater bar and protect your eyes). See how it breaks and examine the color and granularity of the exposed grain. If all is good, finish another blade with the same formula and use the living bejeezus out of it. If it performs well then who cares what the exact Rockwell is?

[SharpEdge0913]

Thanks for the response!

I think was getting a bit fixated on achieving the a specific hardness range based on what I read and was really stumped on how to determine if I hit that range, but you are right. And I really like the feedback on examining the grain and color once broken - can't wait to do that. Great information.

Much appreciated.

[Doug Lester]

Rockwell hardness testers that can handle something as thin as a knife blade tend to run north of $1000, sometimes for even used units. The problem with used units, as I've been told, is that even if they are 100% functional they will eventually need servicing and the reason that these units hit the market is that they are so old that the manufacturer will no longer service them. For reasons like that most of us have to use alternate methods. What I do is try to drive the edge into/through some soft iron wire, like bailing wire, or a thin brass rod and see if the edge indents. If the indentation looks like the edges are curled over then the steel is too soft and I have to reharden and retemper it at about 25 degrees lower. If the edges of the indentation looks like they chipped out then the steel is too hard and I need to just retemper at 25 degrees higher and test again. Of course in either instance the indentations will have to be ground out. Ideally, there should be no more than a slight flattening of the edge with this method.

Doug

[SharpEdge0913]

Thanks Doug. That is a really cool method that I will try.