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Heat treating a crossbow limb

Apestooth

Plastic
Joined
Apr 18, 2024
Location
Oakland
I'm new to this forum so forgive me if this has been discussed elsewhere. I make medieval crossbows and fabricate every part myself with one exception: The prod or bow. When I started out, I used old leaf springs id grind to shape and although they worked, they weren't the safest source of spring steel. If like to start fabricating my own. I have the means to forge whatever steel into shape, I'm just having a hell of a time zeroing in on the process of heat treating into spring steel. First question is: What steel would I use? Second: What is the process of turning it into a reliable spring? Be specific in the process if you can or lead me in the right direction as to where to learn this process.

Thanks in advance.
 
Id think for small pieces of steel,then 'stubs silver steel ' would be OK ..........otherwise you will have to buy a sheet of 1095 ,or somethink comparable.You will either need a proper oven with a pyrometer. and a quench tank ........alternatively you can heat ,quench ,and temper by the old method of burning off the oil.
 
spring steel is a specific high silicon steel alloy. Your best bet for a low volume source is a car or trailer leaf spring manufacturer. buy the blank material, cut it to size and return to the spring manufacturer for hardening and tempering. Heat profile control is important to get a safe spring.

add - otherwise asd john.k says above, you need expensive gear
 
I remember an episode of Forged in FIre when crossbows are made by two contenders to win $10k.

If you like what you see here then the construction part is in the 2nd link. The S5 episode 22 message is wrong. It's episode 28.

The crossbow construction starts at time = 27:00.
 
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McMaster-Carr sells spring steel in a wide variety of dimensions. What you need would cost around 30 to 40 bucks. It is in its hardened state. But it could be annealed, shaped and re-hardened. Rather than use material of unknown alloy like a leaf spring, I'd prefer to start with a known alloy optimized for the purpose.

William Bryson wrote a nice concise book on heat treating and selection of tool steel aimed at the one-off maker.

Denis
 
1095 in spring temper is easily machinable with carbide ,and can be drilled and sawed with HSS tooling at low speed....Silicon steel is used for car and truck springs due to its resistance to abrasive wear and 'digging in' ,properties not required for a crossbow.
 
My spring vendor can fix you up with just about any grade of material from 1095 to Inconel X750. That would be one expensive bow spring!
 
I don't know what size pieces you need for your application, and realize it doesn't answer your question. But was wondering if you have ever harvested any springs from the front end of old Volkswagen cars?

There are multiple pieces 'hidden' inside the round cross tube in old VW's as a kind of torsion suspension. Nice size pieces, not big like car leaf springs, and bonus that they are always in pristine clean condition being housed in that tube with grease on them.

I keep them around for the odd application of monkey business around the shop. Last time I used one was making a well retrieval tool for a local plumber. Just throwing the idea out there for your future possibles arsenal.
 
I don't know what size pieces you need for your application, and realize it doesn't answer your question. But was wondering if you have ever harvested any springs from the front end of old Volkswagen cars?

There are multiple pieces 'hidden' inside the round cross tube in old VW's as a kind of torsion suspension. Nice size pieces, not big like car leaf springs, and bonus that they are always in pristine clean condition being housed in that tube with grease on them.

I keep them around for the odd application of monkey business around the shop. Last time I used one was making a well retrieval tool for a local plumber. Just throwing the idea out there for your future possibles arsenal.
Got any pics of that?
 
john.k,

You're no fun. We got to keep the deer population in check, and keep the hog population under control, too.
Oh, be no more invites to deer leases from the tool companies we buy tooling from, too.
 
Believe it or not,a young woman said exactly that on a television program on the lesbian centric ABC ..........the program did a total hatchet job on well known deer hunter ,making him out to be a homicidal maniac and a blood thirsty savage with dozens of guns.........he was set up believing the program would be a tribute to his prowess as a deer stalker .....silly him .....to be tricked by the most rabidly gun hating journalists on television.
 
Got any pics of that?
R.09bc656af799bf19b0b41c2b338c3822


Learn something every day. Been looking at those old POS for sixty years and never knew there were leaf springs functioning as torsion bars.

jack vines
 
R.09bc656af799bf19b0b41c2b338c3822


Learn something every day. Been looking at those old POS for sixty years and never knew there were leaf springs functioning as torsion bars.

jack vines
So, there must have been a good reason for VW to have designed the torsion bar that way. It seems a bit counteerintuitive to me.

Can someone explain why such a design made/makes sense? Also, roughly, what is the OD of the tube in question so as to get a sense of the dimensions of the individual bars?

Denis
 
IIRC ,the idea was to provide damping of the spring action.........my mother had a late 1950s VW ,with this front suspension .....trailing arms to conventional kingpins......hers was kinda worn out ,and used to go into death defying shimmy if the wheel struck some irregularity ..........every afternoon she would go over a railway crossing that would provoke a shimmy that would rip the steering wheel from your hand...........they a;so had ball bearings for wheel bearings ,the races would get badly brinnelled ,which didnt help.
 
Old VW bits have gone from being junk to high priced ............I wanted some of the steel disc flywheels for a project ,expecting maybe $10 each .......more like $200.
 








 
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