Knife From a Car's Leaf Spring

Intro: 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
Files
Sand paper
Drill press ( or hand drill )
Forge ( or home made forge )
Oven
1/4"x4"x 12" wood. Mine was oak.
Bolts

STEP 2: 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

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

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

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

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

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

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

STEP 9: 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

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

STEP 11: 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

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!!

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.

Cheers

Comments

[bushman89]

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.

[britejrdonnie]

Pro tip, don't use a dang leaf blower that's way too powerful! Unless you are blocking a majority of the duct you will mostly get millions of tiny burning coals shooting into the air! Charcoal or coal likes intermittent blasts of air, but for a quick setup use any easy blowing fan a squirell cage fan works well like from a car or me personally use a bathroom vent squirrel cage fan. I've done the dig a hole poor man's forge. If you find you like forging find some plate steel at least 1/4" thick and some steel pipe for duct work and weld together a forge design you can google plenty of different ones, I've welded together more than 5 different designs. Have fun with it but coal doesn't require a ton of air to get hot enough to forge with. I also have incorporated into my duct work a pipe going straight down to the ground from my forge and my duct is halfway from the fire bowl to the exit of the bottom pipe and I've welded a closable door to divert airflow when I'm not blasting the fireball, it helps wasing coals and keeps you from ruining your work piece by overheating it.

[bobwhite2014]

Chicago screws is the name of handle screws.

[leedog]

The screws that You used Are Chicago screws You can buy at most leather places like tandy

[brianpaul96]

Good looking blade shape! And how well is the blade attracting (or not) rust? 5160 (common spring steel) is usually a very rust loving metal.
And, those special bolts are called Corby bolts :)

[CarlL4]

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?

[zythum117]

Most leaf springs, even the newer ones, tend to have a high carbon content. A food way to check is to run a spark test with a grinder on the metal. Steel has a distinct spark pattern and a higher carbon content steel will give off more sparks that tend to be brighter. Its the best way to tell if a steel is good for forging. Hope this helps.

[zythum117]

This is actually a very bad idea, tempering a blade after a proper heat treat is actually dangerous to the temper of the blade. What you should do is thermal cycle your blade before the quench. Any heating after the quench runs the risk of ruining the hardness of the blade.

But thats just basic blacksmithing 🤷‍♂️

[GotDramaAllergy]

I enjoy watching different methods and results.I list for a junk yard ,salvage yard.I Have access to neat material..Old saw blades,old files,leaf springs from pre-1980's vehicles..Modern I heard of folk having issues with the springs not being 5160..I collected knives from all 0ver the globe,many from 1900-1950 ,made with 5160,and they are world class.Chamorro fro Guam,Kami's in Nepal,Thailand,all use 5160...If it is modern,I heard (Heard) Mercedes is top,then Saab,japanese cars..If Modern American,pre2000 Ford and Jeeps are sure 5160 if pre 2000...I have a pile I just got home of lead springs.Some are smaller width than Cars or trucks,but early pieces,pre 1960's pile it came from.May have been some type of trailer springs.Only 2-3\8 width x 1\4.... If is 5160,MEGA GREAT SCORE...Nice little khukuri typed blade here,nice...Thanks for posting,enjoy watching these..Cheers...

[9rocky]

Try Binding Screws

[Benjosun]

Hey, I'm in Mexico doing volunteer work, so I'm broke but I love making knives with scrap. This was well done, man. Did you kinda guess at the steel color? I don't have a laser heat temperature thing, and I'm still learning. I'm building a mini forge, so I'll be burning and wrecking lots of stuff learning colors.

Is there a chart online that gives some guidance on that biz?

Thanks man

[Claustrophobic Badger]

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]

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]

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]

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

[ChrisB140]

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

[cutprogram1]

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]

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]

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]

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