Question about re-tempering old files

H

Happy Face

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Jul 4, 2010
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Hey guys. I've made some knives before, but never out of files. Trust me when I say I know *NOTHING* about the science of metallurgy - I just do what I'm told :eek:

So, metal is really expensive, but files aren't and they're readily available. I've ground down some files into really brittle knives before, but my question is about re-tempering.

To re-temper a brittle file into a more resilient steel, do you have to re-harden and then re-temper, or just temper it again? Also, do I just temper normally (in the oven) or is there a special process?
 
If you have a bunch of old wornout files of good quality, they're worth playing with. You can retemper them and grind them while they're still hard.

If you're looking at buying new files to use, don't bother. 1084 is cheaper by the foot and you will know exactly what you're getting, so you can dial in your HT.
 
james terrio said:
If you have a bunch of old wornout files of good quality, they're worth playing with. You can retemper them and grind them while they're still hard.
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What I asked was about the re-tempering process, not about whether or not I *can* re-temper them. I want to know what the re-tempering process for files are. Mainly:

Do I just put it in my oven like normal tempering, or do I have to harden, then temper first? are there any extra steps needed?
 
They can be tempered back by soaking in your oven for one hour at 400F.
 
Happy Face said:
Thanks so much Bill. Time to find my dad's old stuff :)
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Maybe start with a few old files from a pawn shop. If you mess those up, go back and get a few more. You only have a particular number of your dads old files. Can't go out and get a few more of dads old tools.
 
Nathan the Machinist said:
They can be tempered back by soaking in your oven for one hour at 400F.
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How hard, roughly, would the file be after that? I've a few files I believe to be 1095 (at least Nicholson non-Black Diamond files are said to be), and since HT is beyond my ability, it could be a source of workable knife stock.
 
Sword and Shield said:
How hard, roughly, would the file be after that? I've a few files I believe to be 1095 (at least Nicholson non-Black Diamond files are said to be), and since HT is beyond my ability, it could be a source of workable knife stock.
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It can be somewhat difficult to predict Rockwell hardness even when you know for sure what the steel is and know its heat history. That said, I would expect a file that was tempered at 400 to be between HRC 60-64.
 
Hm. Interesting.

Think I'll give it a try some weekend. Dead files are free in the shop, so could be a fun way to kill some time.
 
I would strongly suggest a temper of around 450°, rather than 400°. Many files have more than 1.0 carbon, and can be a tad chippy if not tempered accordingly.
 
So what kind of steel is a Nicholson, then? I've read 1095, O-1 and W-2, which should give a final RC of 58-60 at that temp for a temper.
 
Files from Nicholson are 1095. They MUST be normalized, not just a temper in the oven. They have large grain structure from the factory and is not suitable for a knife. To normalize they should be heated to just non magnetic and then air cooled for about 5 minutes. This process should be repeated for a total of 3 times. If you go over non magnetic then the process should be started over. Over non magnetic causes grain growth. Non magnetic is about 1475 to 1550. This is probably the most important thing in knife forging and making. If grain structure is not reduced it will not make a good knife.
 
Mr. Graves. Have you ever broken a Nicholson file and looked at the grain? It doesn't get any better. The grain is velvety fine. There is absolutely no need of normalizing if it is to be a stock removal project. Nicholson files are not common 1095. They have a tad more carbon than 1095 when analized. AND, non-magnetic is always 1414° F, and this does not vary.
 
I'll give it a try over the weekend. Should be able to see the grain pretty well when I snap off the rattail. Thinking a small puuko, 2-3 inch blade. Wonder how much my poor 1x42 will scream.
 
About 4yrs ago I called and spoke to a Nicholson Mfg Representative. She told me that up until the early 1900's they used W1 and after that, 1095. (she didn't specify the chemical analysis) Black Diamond as well as several other brands were all made by Nicholson. I was forging so I wasn't interested in the hardness just the steel type.

I have an awesome PDF that they sent me detailing EVERYTHING about Nicholson from 1878 if anyone is interested.

DanGraves said:
Files from Nicholson are 1095. They MUST be normalized, not just a temper in the oven. They have large grain structure from the factory and is not suitable for a knife. To normalize they should be heated to just non magnetic and then air cooled for about 5 minutes. This process should be repeated for a total of 3 times. If you go over non magnetic then the process should be started over. Over non magnetic causes grain growth. Non magnetic is about 1475 to 1550. This is probably the most important thing in knife forging and making. If grain structure is not reduced it will not make a good knife.
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I can't imagine them having grain growth, Mr Graves... I don't see any type of industry advantage to it. Plus, I have documentation as to how they do their heat treat, which involves clay-like coating to prevent decarb on the individual teeth. They also focus on normalizing and annealing. Great care is taken in their manufacturing process. How are you arriving at that conclusion? I also see a few statements that don't make sense, metallurgically. Grain growth does not occur at the currie point. (which is 1414F) Now, if you really do believe that the non-magnetic point lays within 1475F to 1550F then yes, you are creeping toward grain growth much higher than that. Most of us reference this temperature range as going into full solution for the majority of carbon steels. IMO, I think what you are doing is correct but how you are trying to communicate it to us is flawed. I have great respect for you as a maker, sir... I'm sure it is just misuse of terms.

Rick
 
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lonepine said:
The rattail may not be heat treated the same as the working portion.

- Paul Meske
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The first knife I made was from a Nicholson file, I drilled right through the tail before I tempered it. I don't know if they are all the same though or not.
 
LRB said:
Have you ever broken a Nicholson file and looked at the grain? It doesn't get any better. The grain is velvety fine.
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That's been my experience as well.

The tangs on all I've seen are clearly spot-tempered much softer for toughness.
 
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