Introduction: Knife From a Car's Leaf Spring

Picture of Knife From a Car's Leaf Spring

This is my first instructable so I hope that it makes sense. I will show the basic steps for making a knife from a leaf spring off a truck. Every knife will be different so I will just explain the basic steps and alternative ways of making it if you don't have the same tools that I do.

Step 1: Materials Needed

Band saw ( or hack saw )
Leaf spring
Belt sander
Sand paper
Drill press ( or hand drill )
Forge ( or home made forge )
1/4"x4"x 12" wood. Mine was oak.

Step 2: Design Your Knife

Picture of Design Your Knife

Draw out on a piece of paper what you want your knife to look like. Draw it to scale in the size you want your knife to be. Take into consideration the diameter and length of the steel you have to work with

Step 3: Heat Up Your Steel and Flatten It

Picture of Heat Up Your Steel and Flatten It

Most spring steels from a vehicle will have an arc to it so
You need to heat it up and use a large hammer to pound it flat. This will also require a smooth flat surface.
Also , if you don't have a forge you can make one by digging a pit and lining it with fire bricks and just use a leaf blower with some ducting attached to it leading into the pit. Fill the pit with charcoal and your off to the races. You can also use an oxy acetylene torch. And I even have a friend who used a really hot Bon fire , however the heating is hard to control and keep even that way.

Step 4: Cut Out Your Design

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Cut out the paper template you have drawn and tape it to you're steel. Then trace it onto the steel and cut it out with your band saw or hack saw

Step 5: Grind Your Edge

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Use your belt sander and files to make your bevel and grind your edge. The more gradual the taper of the steel and the sharper angle you can get, the better you're knife will cut.

Side note .... I cleaned up the entire knife to make it shiny and pretty at this stage which proved pointless because I needed to re heat it later and you will too.

Step 6: Drill Your Holes

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The previous picture shows the holes already drilled , it doesn't really matter when you drill them but they will just need to be drilled before you harden your knife.

Step 7: Heat Treat Your Blade

Picture of Heat Treat Your Blade

Here is some quick metallurgy for you. Hope this makes sense. When you originally heated your blade to take the bend out of it , it most likely wasent a super even heat , I know mine wasn't , and you let it gradually cool back to natural temperature over time. This will make the knife soft and it will bend if put under stress. Now what you need to do is evenly heat the entire blade until it reaches a cherry red color , not bright , but a medium to dark red. Another way to know it is the correct temperature is to bring it to non magnetic . This is known by taking a magnet and sticking it to the hot metal. When it reaches the propper temperature , it will no longer stick. When it has reached non magnetic you are going to dunk the entire blade in a container of oil or water. This is known as quenching. I'm sorry I don't have pictures of this process. It all happens really fast and you need to pay attention. I uses olive oil and dunked it in a disposable baking tray. You can use water but oil will give you a more flexible blade. Lots of people say to just use old motor oil but I read a lot of forums about horror stories due to impurities in it so I stayed away .

Step 8: Pretty Knife Ruined

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This is why it's pointless to make your knife beautiful before you quench it lol

Step 9: Temper Your Blade

Picture of Temper Your Blade

Now that you have quenched your blade you are going to want to temper it. Basically now that you dunked it. It has reached a hardened state. But the molecules are under tension from the rapid shock of the quench , so you take your blade and put it in the oven set to about 450-500• for an hour or so. Then turn off the oven and let the blade cool down gradually as the oven does . Some people do that two or three times. I only did it once and haven't had any problems. This causes the molecules to relax and the knife to be more flexible and less proned to snapping.

Side note .... One of my first blades I made , I heated way to hot ...quenched in water and didn't temper it. I threw it at a stump once and it exploded into 7 pieces. So those steps are important.

Step 10: Make a Handle

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Trace your handle out and cut it out with your band saw or hacksaw

Step 11: Drill Your Handle Holes

Picture of Drill Your Handle Holes

Attach one side of the handle to the knife , then drill through the steel holes and through the wood. Then remove it , and repeat the step for the handle slab on the other side.

Step 12: Complete Your Handles

Picture of Complete Your Handles

Attach your handles to the knife and sand them down until it's a comfortable grip in your hand. Then remove them and add either a few coats of oil or what I did which is just a clear coat exterior varathane.

Step 13: Attach Your Handles and Your Done!!

Picture of Attach Your Handles and Your Done!!

I'm sorry but I can't for the life of me remember what these bolts are called that I attached the handle with. They in screw in the middle and one side has a male thread and the other side a female and one end has a slot headed bit for tightening . I'm sure there are lots of different styles but that is what I used.

Anyways that is the completed project . I hope you found this informative . I also made a leather sheathe for this knife and I will do an instructable soon on how to make those.



bushman89 (author)2014-02-19

Thanks again for the comments and feedback everyone. As far as how the spring steel is holding up as a blade material. So far it's been amazing. I have beaten the crap out of it. Baton'd he blade , thrown it. And it retains an edge very well and hasn't fractured or bent at all.

Claustrophobic Badger (author)2017-11-30

Alternatively you can turn your forge blower off and temper it in there as it cools if you don't want to potentially do bad things to your oven

JohnM1233 (author)2017-01-13

Hey Bushman! Nice walkthrough, I found it very informative and useful! Just one question, how's the edge of your knife hold up against other knives?

bushman89 (author)JohnM12332017-01-14

Hey man, I have actually been very impressed with how the edge has been holding up, I gave it a non magnetic quench so it is on the lower end of quench temperatures. That makes It easy to sharpen when it gets a little dull.

JohnM1233 (author)bushman892017-01-14

Ah, I see...I've heard the harder it is to work with, the better the end result!

ChrisB140 (author)2016-08-25

Can you show us a picture of the screws. I didn't understand your description. Would riveting work ok too?

cutprogram1 (author)2014-02-19

How is the leaf spring steel as a blade material? Have heard mixed things about it. Would love to try it out as I have alot of leaf springs kickin around

Phantom0316 (author)cutprogram12016-05-13

I have been told that leaf springs commonly used up through the mid 60's were a simple high carbon steel and work well for knives. Leaf springs after that were commonly complex alloy steels and presented mixed results when heat treating?

Moerdith (author)cutprogram12014-02-24

Just make sure not to over heat the steel. No matter how high the carbon content, if you get the material too hot, you burn the carbon out of the metal.

Wiredfey (author)cutprogram12014-02-23

Spring steel my mentor told me is high carbon steel when makes good blade material cause it holds an edge longer

randyn7 (author)2016-04-10

I believe the bolts are called sex bolts

meteormurat (author)2014-11-24

great ible!leaf spring is a cool choice for a hand made knife ! if you want to temper razor more than the rest cover with mud japanese trick but actually they also use two different density of steel at once!

The 'Japanese mud trick' is properly referred to and differential hardening, by coating the spine in clay, when you quench the blade it causes the exposed area to cool more quickly and the covered area more slowly creating two different crystalline structures. The key to this is a quick hardening steel though, leaf springs are 5160 steel, and that particular alloy is slow hardening so by the time your quenchent soaks the clay and cools the spine there is no difference in hardening. However you can simulate the clay idea by only quenching the edge, and will result in differential hardening.

Alex primitive made it! (author)2016-02-04

Its made with only hand tools and the design its for almost all kind of uses

Alex primitive (author)2016-02-04

You help me a lot with this instructable, im from México and its a little hard have a own forge (excuse my english) i made a knife with a old backyard scissors from Truper, i think its high carbon steel, i dont know but it was really great to make, i dont have pictures cause its on the oven right now, but its really great :)

CarlL4 (author)2015-06-14

I've got a couple of leaf springs I found while hunting we think they're from about 1940-50. So we're also thinking very high carbon content. Do you think they would make good knives?

EarlF1 (author)2015-06-10

Names for the fasteners you used on the handle are: Sex Bolt, Binding Posts, Chicago Screws, Interscrews, Barrel Bolts, Barrel Nut, Partition Screws, Door Closures Bolts, Furniture Screws, Panel Fasteners, Architectural Sex Bolts, Arch Series Screws, Hinge Screws, Display Fasteners, Screw Nuts, Connector Bolts, Threaded Rivets, Grommet Nuts, Post and Screw Sets, Book Screws, and Stationary Screws. I like "sex bolt".

laffinm (author)2014-06-21

Where can you find old leaf springs? I have a lot of project that I want to make that require those, so if anybody knows, please tell me.

BOFH_2 (author)laffinm2015-01-16

junkyards or if someone you know works on cars might have some, swap meets, craigslist. ..

HTWTUSA (author)2014-04-06

Chicago bolts, Bud...Chicago bolts...nice hog.

_Who (author)2014-03-29

It's a very nice knife I really like the design too

hardlec (author)2014-03-26

Nice 'ible.

Kinnishian (author)2014-02-23

Cool instructable!

My only feedback would be to try and consolidate or clarify the information about tempering. It sounds like you tempered the blade, and then annealed it. The annealing is counter to the tempering process, so I don't know what you did it. The only explanation I have is that by tempering in oil you added carbon, but you still wanted it soft so you further annealed it.

But from an outsider perspective it had me scratching my head. I didn't understand why you would have what would be a hardening process (quenching) and then a softening process (annealing)

mookster (author)Kinnishian2014-02-25

I think you might be confused with the terms, and the way steel is treated for knives. The heating to critical (non-magnetic) and quenching of a carbon steel blade will give a hard, but very brittle result. It would hold an edge very well, but if you were to drop it, it would more than likely snap. This level of hardness would be impractical for any kind of real world use.

The tempering process will reduce the ultimate hardness of the blade, but will make it tougher and more resistant.

Hope this is of some use

diy_bloke (author)mookster2014-03-16

but wouldnt it be easier then to do the cooling down in the tempering more gradual then? like in oil instead of water

Kinnishian (author)mookster2014-02-25

Hi Mookster, I think I understand your response. Rather than being explicitly confused, I think you have explained the process- thank you. Annealing and Tempering I suppose were too general of terms

If I'm not mistaken, you are suggesting that the annealing stage is a partial-annealing stage, so not to the full extent of reducing the effects of the tempering.

Kinnishian (author)Kinnishian2014-02-25

I'm also replying to my post to indicate that there have been a good number of more comments explaining the situation. Thanks to all the knowledgeable people here!

Also note, I used annealing and tempering incorrectly. I thought tempering was any hardening but it's more specific than that. Annealing, too, requires a critical temp to be true annealing, so without that I suppose you don't lose the stressed metallic state you're in.

Moerdith (author)Kinnishian2014-02-24

With knives you want the metal to be able to keep an edge, therefor you desire a hardened steel, however you also want the blade to be able to flex and be less brittle, so the spine/dull side is annealed. It can be a tricky/confusing process.

Kinnishian (author)Moerdith2014-02-25

Hi Moerdith, I appreciate your response.But I did not think the instructable was specific however to only annealing the spine.

KemikalzAreFun (author)2014-03-11

It's a pretty knife, think the handle takes away from the look of the blade though. :/

bruce5000 (author)2014-02-27

i have make a few knife like these // i say to stop at step 6 heath like the post alow to cool 2 times its called normalizing then heath treat that was LESS chance of the blade will crack in heath treath

bushman89 (author)2014-02-25

The forge is only necessary if you need to heat up your steel to manipulate it. If you can find a perfectly flat piece of spring steel at the correct size for you then you can cut it out and grind your edge, and as long as you make sure the steel doesn't heat up , by constantly dunking it in water , you won't affect the spring in the steel. But you will be stuck with whatever edge retention that specific steel has. With a forge you can play around with hardening temperatures etc . Not to mention actually forging a knife by shaping it. If you want

Quester55 (author)2014-02-25

Another Great, Blast from the past, a Leaf spring has many wonderful uses, for Swords, Knives, Corn Cutters, as well as the Bows for Crossbows.

I have only one suggestion, Pick up some Gun Barrow Bluing or learn to Brown-Treat, also known as Rust Hardening the steel. It'll last much longer & Never rust again.

te101 (author)2014-02-25

Can anybody help me? is the forge really necessary, if so why is it?

prince-of-weasels (author)2014-02-24

NICE knife^_^ Those screws are called book rivets down here in GA. They come in several sizes.I always used the ground wire out of 12/2 or 14/2 romex house wire to make rivets .Clamp the knife handle on tight with two part epoxy then slide in the copper wire and peen it over on both sides.Another good source for 'free' rivets is ASK the power company guy if he has any 0 or 00 cable scraps in the truck.3 or four inches of 00 will unravel into quite a few 1in rivets......OH with the larger wire you might want to use pliers to hold and peen one end and then take the "nail" and slide it through and X the end so you can get a more balanced 'mushroom' with your[small] ball peen hammer.

jsigl (author)2014-02-24

I would name that knife " The Panty Remover " .

jhowie103 (author)2014-02-24

Hey man nice knife ill definately make one when I get a new anvil for my forge

ardrhi (author)2014-02-23

The process of heating and quenching IS tempering. The process of heating and slowly cooling it is annealing.

grangerknives (author)ardrhi2014-02-24

The process of heating and quenching is hardening.

The process of heating to 300F - 500F degrees for an hour or two and slowly cooling is tempering. (Temps may vary for special purposes.) You do this to draw some of the hardness out of the blade so it is not too brittle and does not break.

The process of heating to critical temp (around 1700F - 1900F) and cooling very slowly is annealing. You do this so it is soft enough to grind, file etc.

It is best to temper in an oven, not with a torch. You can temper by color; but be sure it is straw at the edge. If you anneal until blue at the edge, you'e lost almost all your hardness. Blue or purple at the spine is good. That's called drawing the hardness out of the back or spine. Properly done it can make your knife EXTREMELY break resistant.

Do not ever try to harden your knife with a torch if the blade is longer than an inch and a half. You might luck out and have a relatively functioning blade. But typically, you'll have a low-preforming novelty.

I am no expert, but I have been making knives for 15 years and have been a member of the ABS for about 10. BTW, ALL of the above info is for carbon steel only!

ardrhi (author)grangerknives2014-02-24

Ok, i looked it up again and you're right. There is a tendency in documentation to confuse the terms, and I think the work I learned it from was unclear.

grangerknives (author)2014-02-24

Great job, Bushman! Really nice looking knife.

marhar (author)2014-02-23

Nice job, I learned a lot!

pfrison (author)marhar2014-02-24

So did I, a good andeasy metallurgy course. Thks

cnludwig (author)2014-02-24

Darn, now I'm going to have to make a knife. :)

fetech (author)2014-02-24

I have used carriage bolts to attach handle slabs on hearty blades. If one thinks in terms of rivet, insert a bolt, cut to a length that allows for rounding over with a ball peen hammer.

DJ_Pitachu (author)2014-02-24

Looks great bushman89. Definitely going to make me one as soon as my forge is done.

Skysurfer_uk (author)2014-02-24

I'm fascinated by the hardening, tempering, then drilling. Better to get the knife to the finished profile, but before hardening, drill. Then chuck it in the fire...

snoopindaweb (author)2014-02-23

For smaller blades the leafs from V/W front axle tubes work well.

Silvester10528 (author)2014-02-23

The "bolts" are called "Chicago Screws". They can be found at Lowe's and Home Depot, but you'll find a better selection of sizes and lengths on the internet.

spylock (author)2014-02-23

Its a real nice knife,I like the drop point,and in my opinion the best blade for a survival situation.I would take that blade in the woods.

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