How To DIY Torsion Bar (Kershaw) Advice Required

C

CyberDog

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Jul 4, 2018
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Hi,

I want to make my own Torsion Bar for my Kershaw knife. I live in EU and it is hard to get a spare one from USA. Can you guys criticize my plan on how to make it? And hopefully give some tips.

I plan to buy spring wire (SS304, 1.6mm) from China, it seems it is the only place I can get one. Is SS304 spring steel appropriate for my knife? https://www.aliexpress.com/item/1005002597565313.html

Then I plan to heat the wire and make it soft (what temperature is best for making wire soft?). Then I will design and print a jig for bending the wire to correct shape with my 3D printer.

After I have the final shape ready, I have to harden and temper. I was planning to harden on my gas stove - heat it till it glows red, then quench it in salty water or oil?
Then temper - either in oven at fixed temperature or in boiling oil that starts smoking from heat. How long do I have to temper it?
With a few tries, I hope I will be able to find correct tempering temperature.
I also read that some steels simply don't give good results no matter what you try, but I am willing to take a risk. For the science!


https://imgur.com/a/jaRotwX
 
I don't know much about folding knives, so I cannot speak to that. However, I can tell you that 304 is a non-hardenable stainless steel. The springs made from it are work hardened. Quenching in water may in fact have the opposite effect, as some metals are annealed this way. 304 seems to be one of them, going by a quick search.

Hopefully someone more knowledgeable can chime in on where to look for a more suitable spring.
 
Piano wire would be your best bet, most hobby shops carry it in various sizes.
 
This is my post to a similar question a few days ago:

Round piano/music wire is one popular source for springs. The alloy can range between 1075 and 1095, but is usually around .90-1.00% carbon. It comes in any diameter you could ever need, and is cheap. I buy 1/8" music wire in bundles of ten 36" long rods for $20 with free shipping. It can be bought by the single rod for a few bucks. Many hobby shops carry it, too.
It is already hardened and can be used for a straight spring as-is. Minor bending can be done with pliers. Heating to non-magnetic and letting it cool slowly will soften it so it can be bent with pliers.

It can be forged and bent into any desired shape or coil and then hardened by heating above non-magnetic again and quenching in oil. Tempering is done either by flame or oven ( oven is best). Temper around 550°F or what I call "first blue". The old guys put about 1/8" of kerosene in a shallow pan and set the springs in the pan. They set the pan on the warm forge and when it started smoking, they light the kerosene. They removed the pan ands set it on the anvil and let the fuel burn off. Once cooled to room temp, the springs were tempered.
 
CyberDog said:
Hi,

I want to make my own Torsion Bar for my Kershaw knife. I live in EU and it is hard to get a spare one from USA. Can you guys criticize my plan on how to make it? And hopefully give some tips.

I plan to buy spring wire (SS304, 1.6mm) from China, it seems it is the only place I can get one. Is SS304 spring steel appropriate for my knife? https://www.aliexpress.com/item/1005002597565313.html

Then I plan to heat the wire and make it soft (what temperature is best for making wire soft?). Then I will design and print a jig for bending the wire to correct shape with my 3D printer.

After I have the final shape ready, I have to harden and temper. I was planning to harden on my gas stove - heat it till it glows red, then quench it in salty water or oil?
Then temper - either in oven at fixed temperature or in boiling oil that starts smoking from heat. How long do I have to temper it?
With a few tries, I hope I will be able to find correct tempering temperature.
I also read that some steels simply don't give good results no matter what you try, but I am willing to take a risk. For the science!


https://imgur.com/a/jaRotwX
Click to expand...
If you are in EU you can find SS304 wire in any bigger shopping center for / say wood material , paint , metal , different tools ...etc / in many different Dia. So you can try to make that spring .No need to heat or do anything , just bend wire in shape you want , they are not brittle don t worry .If work good if not you don t spend fortune for that wire , they are cheap .
 
Stacy E. Apelt - Bladesmith said:
This is my post to a similar question a few days ago:

Round piano/music wire is one popular source for springs. The alloy can range between 1075 and 1095, but is usually around .90-1.00% carbon. It comes in any diameter you could ever need, and is cheap. I buy 1/8" music wire in bundles of ten 36" long rods for $20 with free shipping. It can be bought by the single rod for a few bucks. Many hobby shops carry it, too.
It is already hardened and can be used for a straight spring as-is. Minor bending can be done with pliers. Heating to non-magnetic and letting it cool slowly will soften it so it can be bent with pliers.

It can be forged and bent into any desired shape or coil and then hardened by heating above non-magnetic again and quenching in oil. Tempering is done either by flame or oven ( oven is best). Temper around 550°F or what I call "first blue". The old guys put about 1/8" of kerosene in a shallow pan and set the springs in the pan. They set the pan on the warm forge and when it started smoking, they light the kerosene. They removed the pan ands set it on the anvil and let the fuel burn off. Once cooled to room temp, the springs were tempered.
Click to expand...
Thank you sir, I appreciate your response.

Natlek said:
If you are in EU you can find SS304 wire in any bigger shopping center for / say wood material , paint , metal , different tools ...etc / in many different Dia. So you can try to make that spring .No need to heat or do anything , just bend wire in shape you want , they are not brittle don t worry .If work good if not you don t spend fortune for that wire , they are cheap .
Click to expand...
Oh, I didn't know I can find this here. I will look it up in store, but since it can't be hardened and softened, it would be difficult to bend it with 3D printed jig.
 
Get piano wire. Heat it to cherry red and let it cool.
Bend to shape with pliers and vise.
Heat to cherry red and quench in vegetable oil (canola if you can get it.) A file should not cut the hardened spring-if it does, try again.
Polish spring back to natural state.
Heat evenly and gently to just past blue and let air cool.
 
What Bill said is excellent.

Additionally, making a 90° bend is easier if bent while red hot. Use a needle nose pliers and a simple plumbers torch.

A good tip is to use a longer length of wire ( 12" is a good length for smaller springs) and form the spring on one end. This gives you something to hold while heating and bending. You can make two springs by doing it again on the other end after making the first one. Once shaped as desired, cut them off and harden/temper. Pick the one that works best.
 
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