Finishing Carbon Steel


April 13, 2009, 09:23 AM
hey everyone, i've recently started to follow the non-firearm weapons forum here and have been contemplating my first knife. i've picked up some old files from my boss at work and have already taken care of the carbide in them (we were burning brush that day so i threw them into the fire overnight). Although i'm not yet to this stage i was wondering how some of you finished the metal on your knives?
i'm thinking of using some cold blu-ing solution that i have around but was wondering how some people put those interesting designs in the blade that can look almost leopard in style?
perhaps i'd just barely spread some cold blue in a design and wait for it to dry, then hit it with some 000 steel wool to knock it down a touch and repeat till satisfied.


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April 13, 2009, 12:23 PM
(we were burning brush that day so i threw them into the fire overnightBetter go back and get some more files from your boss.
Those are ruined for knife blades.
They are "Toast" now.

You do not want to burn all the carbon out of the steel.

What you want to do is anneal them.
That consists of heating red hot with a torch and allowing to cool slowly.

It removes no carbon from the high-carbon steel.
But it makes them soft enough to work on.

After the blade is finished, you re-temper it to make it hard again so it will hold an edge.

After you burned all the carbon out of the steel in the overnight wood pile fire, you can no longer re-temper them.


April 13, 2009, 01:54 PM
interesting, the guide i saw on knife making did the very thing you say i shouldn't do :(. in order to heat them up and slowly cool them he put them in the fire and let it die down so that they were cooled very slowly. I'd guess by the number of posts you have that you're reputable on this, sad too one of those files was nice and large
ignoring my mistake, would any of you know how to do any of these unusual finishes? just curious


April 13, 2009, 02:03 PM
Well, I could be wrong. Wouldn't be the first time.

I suppose it it possible for the wood fire to get hot enough to burn out the carbon, then cool off and the charcoal add some back in?

At any rate, you have no control over it, and would end up with an unknown carbon content in the steel.

Files normally run about 1% carbon, and there are known ways to temper them for knife blades.

I'd rather start out with a known quantity, and keep it that way by annealing with a torch.


April 13, 2009, 02:05 PM
If the fire didn't hold the steel above cherry red for hours, the steel is not ruined. The outter 32nd or so may be of lower content, but the great bulk is fine, and the outter surface will be removed by grinding anyway. A forged blade is repeatedly heated to yellow, albeit in a more carefully controlled reducing fire, for hours as it's pounded out. You will not accidentally decarburize a file in a non-forced brush fire.

I simply polish my blades to the degree I desire with files and wet/dry papers and polishing compounds. Those smarter and more productive than me use a polishing center (grinder motor with buffs and polishes) for final finishing.

Any carbon steel blade will oxidize in time. Many will put a patina on the blade by soaking in an acidic solution (pop, vinegar, acidic veggies). Nice mottled dull grey look.

I prefer a patina or polished finish. BLuing etc. shows scratches too easily for my liking. Polished finishes require re-touching as the patina grows into'em.


April 13, 2009, 02:55 PM
ah, i'm relieved i didn't destroy my files i am really liking the massive one i got, it's almost a foot long, 2" wide, and 1/4 inch thick. I think i'll probably just polish it as suggested and maybe throw it in a weak acidic solution as mentioned for an hour or so to force a patina. i'll post the pics in the next week or so when i manage to get moving on the project
(gonna make one out of the smaller files first, get better at it before using my king file)
thanks everyone


April 13, 2009, 08:35 PM
I use files almost exclusively to make knives. We use alot at work and the boss says I can help myself to the dull ones whenever I like(he also got a nice Bowie as a bribe). I forge the files into blades so I do not have to anneal the file until after forging and normalizing. When I anneal the blade I heat it to critical temperature(the point that a magnet will no longer stick to the steel) and then place the blade in "heated wood ashes", cover it and let it cool slowly until you can handle it, I heat the ashes by sticking a red hot piece of mild steel in them before hand. I have seen a video on youtube of a knifemaker in England(Green Pete is his name) who anneals his steel by placing it in a fire and allowing the fire to slowly die down. This method seems to work just fine for him. If you keep the files from reaching a bright yellow heat where the steel starts to look like a sparkler in the Fourth of July and anneal them in a low, dying fire until cool you should be OK. Here is an x-file.

April 13, 2009, 08:48 PM
I agree that the files are not ruined, but that there are better ways to soften the files. Now if you did get them too hot, chunks of steel will be missing...

I assume that is not the case.

To make sure these are as soft as you can get heat them up in another fire and this time make them red hot in day light. Then bury them is warm ashes if possible, cold askes if not. Or warm sand, cold vermiculite if you have any, and etc etc..

Don't try to blue the finished piece as blue will wear off.

When you see a patter steel it is wootze steel or damascus.. You can't really expect to acid etch a patter like on some older shotguns and have it last on a knife.

To get that effect you need another type of steel, and with a file the other type of steel could be a softer mild carbon hot or cold rolled steel.

You would weld these pieces to one another, and heat and fold, heat and fold, heat and fold for so many layers as you please.

2 becomes 4, 4 becomes 16 and etc etc... around 128 layers is about what most people do, but you can fold more yet.. There becomes a point where the folding will sort of loose the effect if a bold pattern is desired.

Another way to color steel is in the tempering, which is done after the hardening, but this too will wear off in use.

To see the effect take a ordinary butter knife and heat the tip with a common propane torch until the tip turns bright blue, and then remove all the heat.

Still remain watching as the heat will run back up the blade.

Once the knive has cooled the tip will be a dull gray, the bright blue will be back up the blade somewhere, and many other colors will be back up the blade more, and end in light gold, or light straw.

The blades you make there after should be some where between dark straw and that blue depending on what type of blade you were making.

A flexible blade for cleaning and fileting a fish might be that blue which is spring steel in effect. A fighter might be dark straw little to no flex, but won't snap like glass. Depending on what else you make it could end up one of the other colors, but the color will wear with use.

I high carbon steel to antique you can use all sorts of things to get a dull gray and or pitted dull gray, but dull gray is about it, maybe shades of black.

Tomatoe paste, vinigar, and clorox bleach are some of the ways.

Get a metal container long enough to hold the blade horizontal, and fill it with oil. I prefer used canolia oil for the high (safer) flash point and the more agreeable smell.

Have a steel lid handy in case you do get a flash. (fire)

Just take one of those soft files and heat it orange hot in day light, get the whole thing at that heat some how. I use a forge or oxy actelen torches.

Test with a magnet. When the steel is hot enough a magnet will hot be attracted, and hold the metal at this heat for a few moments.. You must be sure the suface is heated thru to the other surface.

With big plyiers (tongs) dip the hot file in the quench quickly and move the file easy to get the boiling bubbles off the hot steel.

Instantly pull the file out and allow it to cool. Then clamp it in a vise and with safett glass on, long sleeves, and work gloves, slip a pipe over the file and yank hard. The idea is to see the file break like it was glass.

Then take the bigger part of what ever is left, and what ever is left will be as straight as it was, grind a section bright, but do not get it hot. Use a bucket with water and grind dip, grind dip so you can always touch the steel with your fingers and not be burned.

Now heat the area you made bright watch for the colors you learned on the butter knife, and stop long before you see bright blue, while it may appear still.

Aim for the area to end up all that bright blue however, and once it has quench in the oil..

Now chuck that area in the vise and re-do the pipes test. You should find you can bend the steel and when you let go it comes back to pretty straight, of not straight.

Congrats you just learned a lot more than I knew when I started and ruined just one file of many more ruined files. Really

The good thing is not every file will be ruined after you have 40 hours in it.

April 13, 2009, 09:50 PM
thanks for all the advise everyone, i can't wait to get to work on the thing i've even been reading into and considering the finer parts of knife making in terms of shape and technique. i'd like to see my first knife be a little more than just a sharpened file blade... :D
I hate to continue to burden you all with my curiosity but would you be able to tell me how you hollow out the antlers for handles? i often wonder this as they are one solid piece on the outside. i assume there is still a full tang on the inside?


April 14, 2009, 10:27 AM
I always leave a small bit of file teeth in display to 'prove' it was a file. This is a historical thing, which was done for that very reason.

After I have what looks like a knife soft is the time I make and fit the other parts. The blade is all soft untill every part fits, but no rivets are hammered tight.

To do up antler is a nasty buisiness... If you can do it and not puke more powder to you. I can do it though.

The antler and knife tang depend... If the antler ends in a 'Button" you can't exactly have the tang come thru, for show...

If the antler is cut off at both ends the tang can come thru.

And then some people drive the tang thru the Button anyway and make a cap to cover it in a metal.

The tang can be forged out much longer that the file tang is.

What you do depends... To make a hole for a tang it is a good idea to drill 2 holes one above the other no wider than the tang, and chisel out as much as you can with tiny chisels between the drill holes.

Unfortunatley you probably won't be able to chisel in to the antler very deep.

So then you need to heat that tang red hot and press it into the hole, and it will sizzel, scream, and stink real bad.

If you are a married guy and want to stay married do not try this inside the house!

I tend to stop about 1/8th inch before the tang is fully in the antler, then cold drive the last bit which gets a tighter fit. At that point I drill for the rivet, cut off a brass, copper or steel rivet from wire or a nail and trial fit it.

If there is bolsters or end caps I fit these too, but set no rivets.

Then the blade get hardened and tempered, wire brushed clean and the handle is installed... All done, as I sharpen the blade and tape the edge still soft.

April 14, 2009, 05:58 PM
ah Mac thank you very much, and that makes sense that you'd put the antler on by heating up the blade, i couldn't figure out how people were getting square holes in the antlers lol.
got the files back today from the fire-pit i'll probably start the work on thursday


April 14, 2009, 06:11 PM
If I were you I would do some of the experiments to learn how to harden, before you spend a loot of time in getting to the design.

You can do both at once if you like. Leaving the To harden tooling for later while you carve up some steel.

But unless you are just plain into heart break get a junk file soft, then glass hard, and make sure it is by breaking in two then take what ever isthe best piece and temper it. Draw means the same thing.

This picture is a blade I made that cracked just because it wanted too, and in 3 places. The original blade would have been 9 inches of steel and the handle was more.

I was more than just a little bit irritated and threw the cracked blade. The tip came off after it bounced around on the floor some, and I salvaged this from what was left at glass hard. This little devil lives in the brim of a Balmora hat i made, and wear. I use it for light sewwing and slicling elk neck to make mocs.

I was able to forge out the shepards hook, and re harden to glass hard, and didn't bother to temper since it is way to short to bend.

April 15, 2009, 08:19 PM
Macmac is giving you some sterling information. I would like to add to the discussion on drilling an antler for a handle. Several years ago I was in Home Depot looking for some tinning tools when I noticed some drill bits on a rack. They are called "saw bits" mostly used for cutting drywall. They have teeth along the shaft and a normal drill point. These particular bits were 1/4" and are perfect for drilling out antler handles. Unfortunately they are only about 4" long and too short for most handles so I welded some 1/4" stock to them to extend them to 8". I also use the method explained by Macmac which works very well.

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