Tempering a file question - URGENT

M3mphis

M3mphis

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Jan 13, 2011
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I've been reading some discussions going on regarding tempering files for knives. So I'm going to give one a try.

I have a Heller Legend farrier rasp in the oven right now. I plan to do 450 degrees for one hour 3 times. Question - what do I do in between? Do I leave it in oven and turn off to cool slowly? Pull it out of oven? How cool does it need to be before I start next bath?

I'll give this a try and let you know the results.

Thanks, Matt.
 
I water cool between cycles by quenching the blade in a bowl of water and then just turn off the oven at the end... depends how late it is, seems like I always temper at the end of the day. I always go for 2 hours per cycle but I'm no pro at tempering, it is just what I do based off of my research.
 
For the life of me I can't see what makes this URGENT
& it's best to know before you go

but to answer the question

pull it out

let it air cool

put it back in when it is cool enough to hold - touch
 
12345678910 said:
For the life of me I can't see what makes this URGENT
& it's best to know before you go

but to answer the question

pull it out

let it air cool

put it back in when it is cool enough to hold - touch
Click to expand...

Urgent because the thing is about ready to come out of the oven. Should have thought it through a bit more before I stuffed it in there.

Thanks for the help, though.

Matt
 
Tempering for a long time is a good thing from what I understand, you can do a long cycle tonight while you research.
 
If you're trying to anneal the file I don't think this will do. I have some 1080 that was hot rolled but not annealed. I left a piece of it in the oven for several weeks to get heated whenever something was cooked. It was still not soft enough to drill through.

Paul Meske, Wisconsin
 
One hour at 450. Stock file scratches the tempered file but the tempered file skates across the stock file. Must be workin!

P1040827.JPG
 
Relax. Extra time at temperature won't hurt anything, for tempering purposes; an hour is good, most guys go 2 hours just to be sure the steel is evenly heated. The temps aren't anywhere near high enough to cause grain growth or anything like that.

Cooling between cycles can be accomplished by throwing it in the freezer or just letting it cool in air, doesn't matter as far as I can tell.

The purpose of letting it cool to room temp then tempering again is because after the first tempering/cooling cycle, some of the retained austenite will have converted to untempered martensite which is brittle. The second cycle will then temper it fully. A third cycle won't hurt anything.

Paul, leaving it at "bread baking temp" for a year won't anneal it, to anneal you need to get above critical and cool as slowwwwwly as practical - totally different operation than tempering.

M3mphis said:
Must be workin!
Click to expand...

Hah, you posted while I was typing... yup, that's a start. Do it again and you should be in the ballpark.
 
james terrio said:
Paul, leaving it at "bread baking temp" for a year won't anneal it, to anneal you need to get above critical and cool as slowwwwwly as practical - totally different operation than tempering.
Click to expand...

Too soon old, too late smart...

I think I was trying to say something like that. Yea, that's the ticket, I was TRYING to say that but you did it sooooo much better. ;-)

- Paul Meske
 
That depends much on the steel. Many hypereutectics can be annealed enough to drill and file with a few sub non-magnetic heats that will cause the carbon to form spheres rather than platelets. This can be done with file steel.
 
I did one soak at 450 for one hour. Cooled on a rack until almost room temp. Did second soak at 450 for two hours. Cooled in oven. Threw it on the chop saw and got about a sixteenth of an inch or so into the file before I gave up. Its still very hard. I need to temper back more. Just thought I would give you my results to ponder. I will probably try 2 soaks for 2 hours at 500. If that doesn't do the trick, I'll pick up some vermiculite and heat it up with the oxy/acetylene torch. I'll let you know what the results are. I have six files to jack up so this will be an interesting test to see what will work for the novice with limited equipment.

Thanks, Matt.
 
when i anneal files, i build a fire in the fire pit, when its really goin good, i put the files in, have a few drinks, sing some songs, go in really late, sleep, get up in the morning to nice soft cool files

mike
 
M3mphis
It sounds like what you are trying to do is anneal the steal not temper it. We temper a knife or tool steel to acquire a certain hardness depending on its job, otherwise the knife will be too hard/brittle.
But if you want to shape a file into a knife you need it as soft as possible which it sounds like you want to do. So you need to get far higher than 500 degrees. I anneal my files in the forge until they are no longer magnetic, which is roughly 1550 F then place in a bucket of vermiculite to cool slowly.
 
Anneal- make it as soft as possible for ease of shaping somewhat the same as normalizing. Will need rehardened.

Normalize- set the steels carbon to be in shape to harden properly

Harden- take the steel to its critical temp and quench to form Martensite

Temper-condition the martensite and draw the hardness back to the point needed for selected use.

A hard file can be tempered to knife hardness (around 450f) and then carefully ground into a knife. Care must be taken to keep the steel below 450f while grinding so that it is not softened below knife hardness. At this point it will still be very hard, can only be drilled with carbide drills, and will be more difficult to grind, it will file a tiny bit, but wreck the file you use to file it in short order.

If you want to drill some holes for the tang in a tempered file, you can heat the area to be drilled to just past dull red and allow to cool in air. You must keep cutting edge area below 450f when doing this. Wrap in wet rag, stick it in some potatoes, a box of wet sand, whatever.
 
Blindhogg. Non-magnetic is 1414° F, not 1550° F. Just saying, so as to not confuse beginners. If you question that, look it up for yourself. In the case of this being a stock removal project, 1550° is going to grow the grain a bit, unnecessarily, and then require normalizing the grain back down in size, when it already has a perfect size and structure. A few heats just shy of non-magnetic will spheroidize anneal the file where it can be drilled or file worked, and will not change the grain size.
 
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Lrb
Thanks for the clarification. I would hate to knowingly mis-inform, was going off the top of my head.
 
It sounds like the OP wants to soften it enough to work on it but not have to HT afterwards. but if you have tried to cut it with a "Chop Saw" and haven't been able to get through it, I am pretty sure you have already heated it up too much just in that process. Follow the Anneal steps as mentioned above and find a way to HT it afterwards. As stated you are dealing with an unknown steel, so results will be mediocre. but it all is definitely great practice.
 
RyanW said:
It sounds like the OP wants to soften it enough to work on it but not have to HT afterwards. but if you have tried to cut it with a "Chop Saw" and haven't been able to get through it, I am pretty sure you have already heated it up too much just in that process. Follow the Anneal steps as mentioned above and find a way to HT it afterwards. As stated you are dealing with an unknown steel, so results will be mediocre. but it all is definitely great practice.
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Yeah, I was thinking of tempering it back enough to grind it and not HT. I thought I would try to profile it with a hack saw, but it was still so hard that I threw it on the chop saw (knowing that it would be way too hot for my original plan) to see just how hard it is. I don't think I have the patience to grind it that hard. Besides, how many belts do I really want to ruin!? :) I'm still wondering - what is the best way to profile something that hard without making lots of heat???
 
Any steel at knife hardness is not going to hacksaw or file without a very special saw blade or diamond files and those would be s l o w. Do, you have a 4 1/2" grinder and some thin disks? The .045 thick disks will cut it fast. Also, if you cut a straight line 1/3 through it will snap off on the line. Just dip the steel in water every few seconds and leave some steel to grind away to get your final shape. You could also profile and bevel the blade pretty fast with a 36 grit belt. The tang area you don't have to worry about the heat much. What do you have for a grinder? With a good grinder and belts a hard file isn't going to grind all that much harder than soft steel. But, a LOT more care and time will be needed to keep it from over heating.

If you are trying to save money by using a file and don't a have good grinder or anyway to anneal and harden it properly its a hard way to go. I suggest you buy a piece of 1084, 1095, O1 or 5160. Then, cut file or grind it to shape leaving it a dime or so thick at the edge, and sanded to say 240 grit. If you get a 3' bar you will get 3 or 4 shots at coming out with a piece that looks like what you really want. Then sent it to me with return postage and I will harden it and temper it for you and send it back. Then you can finish it.

Making good knives may be many things, but, its not easy or cheap. I have a pile of at least 50 used Nickleson files and mostly they stay in that pile for a reason.
 
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