Forge a Knife

A quick knife with few tools and some prep work.

There are a lot of pictures, and I hope they help explain what I am doing. Sorry, no action shots. I don't have anyone to hold the camera : )

Let me know what could be clearer, and what I should take out. Doing it is so much easier than trying to explain how to do it for me.

Step 1 Where to begin...

Since this is going to be a knife, we need some decent (if not good) steel. Hmmm, well, here's some bits of high carbon steel. All of these pieces started out as springs, some have been worked a bit.

If you start with a 'new' coil spring from a car, it will need to be cut down. I find it easiest to throw the coil spring into a bonfire, let it get hot, then cool off (anneal, or soften, or remove the temper) then cut it with an angle grinder
http://en.wikipedia.org/wiki/Angle_grinder
or high tension hacksaw (worth the extra few dollars).
http://www.stanleytools.com/catalog_images/mid_res/15-113_mid_res.jpg
http://www.stanleytools.com/default.asp?CATEGORY=HACKSAWS&TYPE=PRODUCT&PARTNUMBER=15-113&SDesc=12%26%2334%3B+High+Tension+Hacksaw
If you skip the annealing, you use up a lot more blades and elbow grease whether you use the angle grinder or hacksaw. If you use a flat spring from a car, you don't have to anneal, but I find that kind of spring a bit awkward to hang on to.

NOTE: protect your eyes! The angle grinder throws off more sparks than a firework and they get into the most painful places.

NOTE: cut metal is HOT! An angle grinder is faster, but all those sparks are burning steel. Whatever you are cutting will get hot, even if using a slow hacksaw.

NOTE: cut metal is SHARP! Even a flat edge has burrs that will grab your skin and tear it open.

I did part of this last fall, so I don't have any pics of the annealing or cutting : P But here's the end result.

I'll be using the big round piece.

Comments

[oldanvilyoungsmith]

"all the tongs I make look funny"
I'm with you, I can't seem to get any good ones yet, I use a large pair of channel locks and some tongs somone else gave me.

[jtobako]

I don't like the bend in channel locks, but have used them.

[jadronx]

blacksmiths secret weapon, vise grips!!

[0087adam]

what about squeezing it with a vise to make it uniformly flat?

[jtobako]

Several problems-finding a vice powerful enough to do it cold or fast enough to do it before the heat is transferred to the vice. Either way, you end up letting a big tool do all the fun stuff, and you are just left with 'stock removal' (grinding off everything that doesn't look like your knife). Drop forging is what you are thinking of, stick a chunk of hot metal into a die that smashes it into shape. Of course the press starts at something like 100 grand plus another 20 thou for each different die...numbers are just guesses, but still several orders of magnitude more than I have for a hobby ; )

[iamjtg]

Those numbers are very accurate.

[curvy77]

iv made some knives from the bottom of my dressar drawer( mid quality steel) and folded them over a few times. but after i forged they seem to rust more then before they were intrduced to heat. anyone know why? o and nice forge. alot better than mine.

[hifatpeople]

arent you supposed to fold the steel like a hundred or so times for soemthing?

[thedingwing]

That is an ancient Japanese technique for making Samurai swords. The metal was folded 12 times, giving it 144 layers that could be seen after polishing and sharpening.

[kthompson-2]

no they would fold them about 50 - 300 or more folds

[jtobako]

Except that the steel used wasn't homogeneous to start with, and so had 'personality' that worked it's way in (more-so than the Indian wootz, or damascus steel) . Plus, there were several methods of layering the steel-the soft center surrounded by layers of harder steel or a hard edge applied (welded) to a softer back...and no folding after that...

2 layers folded becomes 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192 layers after folding 12 times. It's 12! (factorial) not 12x12 (squared).

[jtobako]

Why? I'm starting with good steel, not the crap that comes out of a primitive smelter.

The early iron-smiths had to average out the carbon content of what they had, and so had to mix the metal by folding it. Bessimer fixed that.

[PastTheVoid]

Brick is mostly made of cement.

[jtobako]

Pavers are made from cement.  Brick are made from fired clay.  You can tell the difference by looking at the surface (sometimes you have to look closely), cement has a sandy and gravel texture, clay may have grog (pre-fired clay) in it but the texture is much smoother.

[kthompson-2]

do you mean fire bricks??

[chewingum]

grandissimo !!! ... you are great ;-)

[usb key]

what are you using for fuel? Just plain wood, or is that (Char)coal underneath?

[jtobako]

All three : ) I have a limited supply of (mineral) coal that I'll use when I don't want to keep feeding the fire, but mostly charcoal from old campfires (scout campfire pits where the fires aren't allowed to burn out are good sources) and wood.

[SDTruckSprings]

I was reading your article on the war sword and how it was made with old leaf spring metal, to create swords/knives/daggers, and found it very interesting. I work for SDTruckSprings.com and being
that we work with these, things all day. Its nice to see them put use rather just sit there at a scrap yard or in the wear house, and with customers always buying new leaf springs --- obviously they have
old leaf springs; so we decided to write about a trend we've spotted on your site and show our customers what some are doing with their old leaf spring metal. So we wrote an article about it which you
can find here. Hope you enjoy!

[Wooginator]

 I'd like to know where you got your  big piece of metal to use as an anvil.  Anvils online seem to cost a lot of money, more than I particularly feel like spending, or else their reviews say they're crappy.  And I can't very well go and saw a piece off the railroad track, I think it might cause some problems.

[hackmattr]

Harbor Freight has a couple of anvils.

[jtobako]

Until you KNOW which batch you are buying from, they are just ASO (Anvil Shaped Objects)-a few are good steel, most are soft cast iron. Steel will keep it's shape under hammer blows, iron will absorb the energy from the hammer and make everything twice as difficult while becoming dented and smooshed.

[$0m3_0n3]

Yup, i bought one and it's definitely iron. Also the foot broke off :(

[jtobako]

Yep, anvils cost a lot, and good ones tend to cost more.  Scrounge, look where others get rid of stuff, think creatively.  There's a professional knife maker (Lively Knives?) who makes his anvils out of a chunk of 4x4 steel and a bucket of cement.  You should be able to do the same with a piece of crank shaft or solid axle.  You might even be able to do the same with a sledge hammer head.

I think someone on Anvilfire said that an anvil should be at least 25 times heavier than the hammer you are using, and I've found that lighter anvils bounce around : )  For knives and swords, mostly you need a flat surface-use an angle grinder if you have to-and occasionally a chunk of something round or a rounded edge on your anvil to do some of the transition areas.

[spenny1972]

also a good source for anvils are railyards.most railworkers would help you by giving you a chunk of rail. this can be ground(either with angle grinder or professionally)into the shape you want.

[spenny1972]

in response to wooginator: using a torch is not recommende as the tempering would happen too quickly. and yes you can use a sledge hammer as an anvil but better to cut a hole in a large stump slightly smaller than(like almost exact size)heat the one end with a torch hot enough to scorch the wood and pound the sledge in straight. using concrete would be noisier and would break almost immediately. if you want to see a sledge used as an anvil go to kukri house international and look at the process their smiths(kamis)use.

[spenny1972]

to have more control over the tempering process, heat a 1/4" thick rounded steel plate up to 430- 530 degrees farenheit and rub the body of the blade around until the polished edge of the blade begins to change colour.rubbung both sides of the piece around. dark "straw" yellow for knives and light purple for larger cutting implements like swords. when desired colour is reached quench along edge of blade(for single edge knives)and straight down for double edged pieces.(to prevent warping).

[netbus]

Do I need an air source to blow on the fire and make it hotter? I heard I need...

[jtobako]

Hotter than what? A camp fire will heat metal to red, but it takes a long time. If you add air, it heats faster.

[netbus]

Guys I saw this on eBay and I plan making a replica of it - http://cgi.ebay.com/SMALL-HANDFORGED-THROWING-KNIFE-VERY-COOL-/170498516463?cmd=ViewItem&pt=Collectible_Knives&hash=item27b280e5ef Is it just the cam, or is the steel kinda blu-ish? If it is, can I give my steel that color?

[jtobako]

That looks like the camera lighting adjustment. You can get some color when heat treating, but it has to be with clean metal, not fire-scale. Think old-gun blue or good, old-fashioned watch blue.

[netbus]

Wow that was quick! I'll try... Also I'm not sure if I'll be able to get a car spring, I'll find a file instead. Are these these basically the same quality? I heard that files are perfect for making knives...

[jtobako]

OLD files-or at least made by a decent company (like Nicholson or Diamond) will be. I had one that was case hardened and didn't start out sharp...

[Wooginator]

Also, would it be possible to use a blowtorch to accurately heat and then work specific areas?  There wouldn't really be any difference assuming the torch can heat the steel to the proper temperature, right?  Oh, and could I cut the head off a large enough sledge hammer and stick it in a bucket of cement and use that as an anvil?  Sorry for all the questions, don't mean to be a bother.  You just seem very knowledgeable on the subject.

[jtobako]

I'm used to making do with next to nothing ; (

A torch can work, but you loose a LOT of heat without something to reflect it back into your work (like the walls of a gas forge).  Try making a bean can forge or even a pile of clay brick (NOT cement pavers) or fire brick to hold the heat around the metal.

If you use the sledge hammer, make sure the surface that's up is flat-ish, or your metal will have weird marks you'll have a hard time getting rid of : )

[manicmonday]

How would you temper it if you want it to be springy like the spring it originally was?

Thanks

[hanzokendo]

Drawing the back side of the blade along a pipe will weep away the heat causing less trauma to the crystalline structures during the quench, giving the knife a softer spine.

[jtobako]

"Trauma" to the crystalline structure would be work hardening. If I wanted to do a one step quench with a softer spine (differential hardening) I would only quench the blade portion, leaving the spine out of the quench to cool more slowly. I suspect (from personal experience) that the time taken to try to cool the spine would cool the blade to much for proper hardening due to the difference in cross section (the thin blade cools faster than the spine, so it has to get into the quench FAST).

[ninja guy]

http://www.instructables.com/id/How-to-wrap-a-samurai-sword-handle/Here is how to wrap the handle like a samurai sword

[jtobako]

'Cept there's no hole for the pin. And no room for one on a rat-tail handle.