Annealing a few file knives.......

[lockbuilder]

Hey All,

First post here!

I do a lot of heat treating and annealing in my everyday work as i build 18th century rifle locks for a living.

I am playing around using some of my old files to learn bevel grinding and making a few knives for the the first time. I used a few Nicholson, 6in mill smooth files to make up some blades.

I annealed them by going bright red and then submerging them in lime until cool. Then ground all my shape and bevels.

I then hardened using Lubsquench 1021 which is what I use for my gun parts.

Then I annealed twice at 400 for an hour each time. Got a nice deep straw color. But these things were still very hard!

Just for giggles I put them in my Thermolyne HT oven for an hour at about 550 and brought them up to a peacock blue.

Still so hard a file practically skates across the surface.

What now? I know this stuff can be softened as I did it initially. Should I bump up the annealing temperature incrementally? Anyone have a recipe that worked for them with Nicholson files?

Thanks much,

CE

 

[KnuckleDownKnives]

My first knives were made from files. Annealed in a wood fire and let the fire burn out over night. grind and shaped blade, heated to non magnetic, quenched in 130* canola oil. tempered at 400 for an hour twice. Gt the straw brown color you are referring to and they make a very strong very sharp blade with very good edge retention. I would stay at 400 to 450. You don't want a file to really bite into them at this point. When HT and quenched they are brittle. Heating to 400* takes the brittleness out of them and leaves them very hard.

I'm sure someone with more experience than me will chime in.

 

[A.McPherson]

So I think you're mixing up terms, which will make it harder for you to get good answers.
The process of making steel soft enough to work is annealing. The process of softening a blade (or anything really) to make it less fragile is called tempering. When you are finished tempering, it will still be very hard. But probably not so hard that a file skates. How good is your thermometer? Are you sure you were at 400?


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[andrewh2011]

To file a file knife you need to get it up to temp (not sure what temp I think it would be 1550ish ????)then slowly cool it usually people just stick it into vermiculite

 

[lockbuilder]

So I think you're mixing up terms, which will make it harder for you to get good answers.
The process of making steel soft enough to work is annealing. The process of softening a blade (or anything really) to make it less fragile is called tempering. When you are finished tempering, it will still be very hard. But probably not so hard that a file skates. How good is your thermometer? Are you sure you were at 400?


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Yes, you are correct! I meant tempering. My bad!

Yes I am certain of my temps. The pyrometer on my ht oven is off so I confirm with a infrared and a thermometer.

And it has been my experience that I can usually cut a commercial blade with a file (at least a bit) which is why I was using that as a "gauge"

The gun parts I work with are 1095 and 01 and are usually tempered to 600*. These cut a bit easier (as they should) with a file than most knives I encounter. Anyhow that is how I'm"gauging" things as i don't have another way to test the hardness.


Thanking you all so far!

 

[Don Hanson III]

450 to 500 is a good temper temp for file knives. Best for them to be hard enough that a file can't cut them.
Why would ya want them any softer?

 

[lockbuilder]

450 to 500 is a good temper temp for file knives. Best for them to be hard enough that a file can't cut them.
Why would ya want them any softer?

Okay, that helps a lot. It isn't a matter of wanting them softer so much as having someone who knows, tell me what you just did. Thanks!

I'm going to go ahead and just finish them up and see how they come out.

Best!

CE

 

[Don Hanson III]

Okay, that helps a lot. It isn't a matter of wanting them softer so much as having someone who knows, tell me what you just did. Thanks!

I'm going to go ahead and just finish them up and see how they come out.

Best!

CE

Well, you're on the right track, they should make good knives.

 

[Don Hanson III]

One the next one, when you start, heat to a dull red and let air cool.

There is no real good reason to do a full anneal or a 'slow cool down' on a file to start a knife.

 

[samuraistuart]

There are a few ways to anneal the file:

As Don said, bring to dull red heat and let it air cool (no slower than still air for high carbon steels). This is a quick way of doing a lamellar anneal and it will provide good results.

Or, do a bladesmith spheroidizing anneal. Starting with a file that has had no other heat treat operation done to it, simply "temper" the file at 1200F for 2 hours. This will "spheroidize" anneal the file, making it super soft for easy machine work. This will require a short soak, 10 minutes max, to redistribute the carbides for hardening.