How to heat treat a file?

[Shaggy8675]

I got a great big file this week I want to use to make a razor out of. But of course the file is still hardened. Who can help me with what temperatures I need to get it soft enough to work with and for how long it would need to be at that temp?

And after softening and working the metal, what would the best temps be to harden again and what process? Oil cooling, air, water etc?

I can use a professional grade heating oven to heat so it's down to the degree and minute precise if needed.

Who could help me with some hard needed advise

Thanks.

 

[Kroo]

Hi Shaggy,

Ideally you need to contact the manufacturer of the file and find out what steel it is - that would allow for a more precise/specific regimen - although I have to say carbon steels are quite forgiving, within reasonable limits...

It is likely the steel is 1095 or one of it's equivalents, so I will give you that one. For annealing, run it up to 1650 F (890 C) and soak it - leave it there for at least half an hour per inch thickness and a minimum of 15 minutes for thinner stuff. Let it cool down slowly - about 25F per hour, to about 900 F and then you can let it air cool to room temperature. In practice, soak it proper at 1650 F, switch the furnace off and just let it cool with the furnace, or if you need to remove it sooner - take the hot blade and stick it into some fine ash and let it cool in that.

To harden, reheat to 1650F, let it soak for at least 15 minutes, or 30 minutes per half an inch of material thickness, and quench in oil - old motor oil will work just as well as the more expensive, cleaner quenching oils. Move the blade around in the oil to prevent hard and soft spot forming due to smoke pockets forming on the hot blade in the oil. If you want less smoke formation and a little faster quench, mix your motor oil 50/50 with cooking oil (sunflower/canola) or 50/50 with diesel. Keep moving it around in the oil for about 30 seconds or so and then take it out and let it air cool to room temperature. I like putting it in the bench vice at this point, as the steel is still "plastic" to an extent for a minute or two, and this takes care of any slight bending that it may have suffered. The steel from the vice acts as a heat sink and draws the last bit of heat out of the blade.

Clean the blade by sanding/grinding and temper at around 350 to 400 F. Forget about times - check the blade physically every few minutes - you have seriously diverse thicknesses - so the edge is going to heat up MUCH faster than the spine - watch for golden yellow oxide to form on the steel - angle the blade against the light and you will see it - WHEN THE CUTTING EDGE gets to that color, dip the blade in water, sand clean and repeat. If you wait for the whole blade to get to golden yellow the cutting edge is going to be blue or beyond and the spine not yet golden - meaning the spine is hard and the cutting edge (relatively) soft.
You can also temper using a gas flame - run a smalllish flame up and down the spine with the blade perpendicular to the flame and watch for the edge to turn golden yellow, and quench in water.

If you want to soften the shank and tang, stand the razors blade in a tin of water, using a piece of wire to keep it upright, and heat the tang and shank to dull red with the gas flame, take it out with a pair of pliers and stick into some fine ash, tang first but cover the total razor, and leave for a while to cool down.

Hope this helps

Willem

 

[Kroo]

Sorry, I forgot to add, one way of going about this is to cut a piece off the file, run it through the heat treatment cycle (anneal and re-harden) and see what results you get, before you commit the whole file...

 

[Shaggy8675]

Thanks, this helps a lot.

The file is a pretty old one, so a manufacturer is hard to be found. But those temps should indeed be not much of a problem. I'll give that a try. I'll program the oven to 890c let it sit for an hour and than cool overnight.
Does it make a difference iff you were to put the file in, start from 0c to 980c and back to 0c, or do I fire the oven to 980c drop the file in and than let it cool? ( and to think I was educated as a metalworker haha, but that was over 25yrs ago )
I imagine dropping a cold file in a hot oven might cause stress/cracks or things?

But thanks so far indeed. Loads a good info to work with

 

[daflorc]

Hi Shaggy,
Ideally you need to contact the manufacturer of the file and find out what steel it is - that would allow for a more precise/specific regimen - although I have to say carbon steels are quite forgiving, within reasonable limits...

It is likely the steel is 1095 or one of it's equivalents, so I will give you that one. For annealing, run it up to 1650 F (890 C) and soak it - leave it there for at least half an hour per inch thickness and a minimum of 15 minutes for thinner stuff. Let it cool down slowly - about 25F per hour, to about 900 F and then you can let it air cool to room temperature. In practice, soak it proper at 1650 F, switch the furnace off and just let it cool with the furnace, or if you need to remove it sooner - take the hot blade and stick it into some fine ash and let it cool in that.

To harden, reheat to 1650F, let it soak for at least 15 minutes, or 30 minutes per half an inch of material thickness, and quench in oil - old motor oil will work just as well as the more expensive, cleaner quenching oils. Move the blade around in the oil to prevent hard and soft spot forming due to smoke pockets forming on the hot blade in the oil. If you want less smoke formation and a little faster quench, mix your motor oil 50/50 with cooking oil (sunflower/canola) or 50/50 with diesel. Keep moving it around in the oil for about 30 seconds or so and then take it out and let it air cool to room temperature. I like putting it in the bench vice at this point, as the steel is still "plastic" to an extent for a minute or two, and this takes care of any slight bending that it may have suffered. The steel from the vice acts as a heat sink and draws the last bit of heat out of the blade.

Clean the blade by sanding/grinding and temper at around 350 to 400 F. Forget about times - check the blade physically every few minutes - you have seriously diverse thicknesses - so the edge is going to heat up MUCH faster than the spine - watch for golden yellow oxide to form on the steel - angle the blade against the light and you will see it - WHEN THE CUTTING EDGE gets to that color, dip the blade in water, sand clean and repeat. If you wait for the whole blade to get to golden yellow the cutting edge is going to be blue or beyond and the spine not yet golden - meaning the spine is hard and the cutting edge (relatively) soft.
You can also temper using a gas flame - run a smalllish flame up and down the spine with the blade perpendicular to the flame and watch for the edge to turn golden yellow, and quench in water.

If you want to soften the shank and tang, stand the razors blade in a tin of water, using a piece of wire to keep it upright, and heat the tang and shank to dull red with the gas flame, take it out with a pair of pliers and stick into some fine ash, tang first but cover the total razor, and leave for a while to cool down.

Hope this helps

Willem

Great post

 

[MileMarker60]

IMO I would not take file steel to 1650 for hardening. That is over shooting the temp a good bit which can create grain growth.
The same can be said for the soak time. Simple steel requires little-to-no soak time, that will create grain growth also.
The file is most likely just a simple steel, so keep it simple
Anneal it for easier cutting and grinding - 1475F and cool at a rate no faster than 50F per hour.
Cut, shape, filework, pivot hole... Take it up to around 400 grit.
Normalize - 1575F, soak for 5 minutes and allowing to cool in still air.
3 times, this will help to prevent warping and crack during hardening
Hardening - 1475F, soak for no more then a couple min. at most.
You can quench in cooking oil with out a problem. Warm it up a bit, 120-140F.
Once you can handle the razor take it straight to temper. Give the razor a quick soap and water scrub then into the oven, 400-425F for 1hr, twice.

Hope it helps

 

[Kroo]

Hi Shaggy, glad to help. Put the file in the cold furnace and let it heat with the furnace.
MileMarker has a point - don't soak the file for more than about 15 minutes when annealing.

He also has a point about the temps. The temps I gave you are for 1095 - the temps he gives are compatible to O1/K460. There is one simple way of checking this - heat the file up to around 1475 and test it with a magnet - if it has lost it's magnetism (ability to draw the magnet) then let it sit at that temp for about 15 minutes and let it cool slowly with the furnace. If it still draws the magnet at 1475, take it up to 1650 and test again - or test again at 1550 and then 1650 - when it loses magnetism, let it sit there and soak.
I have no idea how thick the file is but for something around 6mm which is about what you need for a razor, but MileMarker does have a point about a long hardening soak - a 15 minute soak should be seen as absolute max - you might well get better grain structure and so better edge taking and holding, with a 7 to 8 minute soak.

(When testing with the magnet, don't touch the magnet directly to the hot steel, put it on a piece of steel and bring that to the hot steel - direct contact might shatter the magnet)

 

[MileMarker60]

The HT info I posted is for 1095 (and will work for almost all simple steels, ie: 1080,1084,1086v, etc..)
O1 is a little different but not much, most of the difference is the soak time before quench.
I can say none of the simple steel I listed above needs to go over 1500F, if you do your only creating problems.
I'm not a HTing pro.... but I have made a few razors

 

[Kroo]

Interesting. Like you I am no HT "pro" but also like you I do quite a lot of it on knives - I don't use 1095 much, as it is not readily available over here (use mostly O1/k460, 52100 and 5160), so the temps I quoted I got off a spec sheet from a collection I have for different steels. Did a quick check on the 'Net and I see there are at least 3 different temp ranges put forward with yours, around 1475, being most common.

Shaggy, as a general rule of thumb, rather under heat than over heat the steel a bit, so see 1475 as your aiming point - the spec sheet I have may be a little over optimistic in it's temperatures. But seeing as we don't know what steel it is precisely, rather use the magnet to test from around 1400F.

 

[Shaggy8675]

Thanks a lot guys. At least now I have some good guides and tips to do it and what to look for.

 

[Kroo]

Please let us know how it goes - and post some pics

 

[Shaggy8675]

I'll try to post some pics. I'm not allowed to take pictures at my workplace/bring cellphone so the actual heat treatment I can't show. The result of grinding I can of course.
As for now, Heat treatment seems to have gone well. Put it in the oven and let it cool overnight. Steel is softer now. Roughr grinding has been done for the most part. But I'm running in to the limitations of my grinder



But here are some crappy phonepics


2013-12-27 22.38.43 by Remco van de Sanden, on Flickr


2013-12-27 22.29.14 by Remco van de Sanden, on Flickr

 

[bluesman 7]

Looking great so far. From the picture of your grinder, it looks like the guards on the contact wheel are really restrictive. They seem to have a larger radius than the wheel. How did you do the concave small radius curves like the thumb groove?

 

[Kroo]

Shaggy, looking really good so far - I LOVE the design!! Good point bluesman makes - did you remove the guards? Aren't you leaving yourself a lot of grinding to do post HT? Looking forward to seeing how you progress!

 

[Shaggy8675]

Thanks guys,

Indeed I "modified" the guards on the grinder slightly with a hacksaw haha. The problem is I can get the steel from right to left, but not from left to right, the motor is in the way. But I'm goin to try and switch the belt part to the other side. Takes 3 screws to try it, so I'll see. Want to make myself a good beltgrinder ASAP though.

Bet the radius of the thumb was mad by the top wheel. First grind 90% on the stone, then the rest on the top part. Goes pretty well.
But for now, it seems to be working as well as can be expected from a setup like this. But I got time and patience, no rush to get it finished.
Biggest problem is the lack of fine belts. I can get up to 100 grit belts, from that point on it's all by hand, or making my own belt with tape and waterproof sanding paper.

 

[bluesman 7]

I like the look of the file pattern on the tang and spine, but on the spine it's going to be really hard on strops.

 

[Shaggy8675]

I'm going to grind/flatten/polish that a little so it's not aggressive any more

 

[Soldierdan]

I can get up to 100 grit belts, from that point on it's all by hand, or making my own belt with tape and waterproof sanding paper.

The shipping might not be the best situation to your area, but these guys have all manner of grit level belts.

https://www.econabrasives.com/products.php?pro=6

 

[Shaggy8675]

Thanks Soldierdan,
But indeed. The shipping will proberbly be the bottleneck. But thanks for thinking along

I managed to put the belt on the other side. And it works great Even made a crappy cellphone video to show haha

 

[Slash McCoy]

First of all, Shaggy, that's a nice looking project. You ought to do a regular Western style razor to go with it, so you have a fixed handle type and a matching scaled type razor in a set.

Vintage files definitely better. I compare the old Nicholson US made files to the new Nicholson imported files, and it is like night and day. The new ones just don't last. I can only imagine how much better the steel of the old files would be for a razor, compared to the newer cheaper files.

Kroo and MileMarker, great posts. Great information.