Mainspring Fabrication

[Anthony]

Have a lock that needs a mainspring. Will have to make it. Can either forge one from 5160 or machine it from 0-1 . Curious on thoughts & or opinions on durability. Thanks.

 

[Phil Coffins]

I’ve used O1 for springs, the trick is in the heat treat.

 

[dave_person]

Hi,
Use 1075 steel. It is far more forgiving than O1 and better than 5160 for springs.

dave

 

[Anthony]

Hi,
Use 1075 steel. It is far more forgiving than O1 and better than 5160 for springs.

dave

 

[Anthony]

Great work. Thanks.

 

[ZUG]

I use O-1 for most of my knives that I make and have all thickness of the stuff. I also use 1084. I find the best material to make flat springs from is 1075 like Dave says. You can buy it online from NJ Steel Barons for cheap in different thickness and widths.

 

[dave_person]

Hi Anthony,
I would urge you to forge the spring and not machine cut it from a solid block. It will be stronger without the need for extra thickness at the bend.

dave

 

[James Kibler]

I would agree about avoiding O1. It can certainly work as a spring, but requires significantly higher temper temperature.

5160 is a good spring material. Basically the goal is to get it somewhere between 40-45 HRC. You can look up heat treat cycles for each material. Remember tempering temperature will be different for different materials.

 

[wiscoaster]

OP didn't specify what lock and what firearm, but Paul Ackermann at https://www.ackermannarms.com/ fabricated a frizzen spring for me, so that's probably something he can do if it's one of the firearms he supports.

 

[James Kibler]

Hi Anthony,
I would urge you to forge the spring and not machine cut it from a solid block. It will be stronger without the need for extra thickness at the bend.

dave

I believe this is way overblown and largely insignificant. I’ve done some stress analysis based on the variation in mechanical properties (anisotropy) with grain direction and it’s not much of a concern. I don’t believe any increased size at the bend is required, but I do this for added safety margin.

Out of thousands and thousands of mainsprings we’ve made, not one has broken to my knowledge.

I would argue the forging process in itself, would introduce opportunity for error and result in a much higher scrap rate. For example overheating material, bending when too cold, thinning of material based on the bending process etc.

Another interesting fact is that all of the fantastic locks Jud Brennan makes have mainsprings cut from the solid and not bent.

I firmly believe the advantage of a formed spring for a mainspring is negligible at best and probably more likely to cause problems.

 

[GREENSWLDE]

I always use CS65 for Gun Springs.. Make your self a "V" block and a narrow V punch with a small
Rounded end to fit the the double thickness of the V Bloc to allow for the metal thickness.. After hardening S65 put it in the lead pot at melting temp.. to temper. O.D.

 

[Flint62Smoothie]

What gets me about spring making is ... I went to ~5 sources (e.g., Track, Kit Ravenshear, The Rifle Shoppe, Dixie GW, etc.) and got 8 recipes, all quite different!

 

[Phil Coffins]

I believe this is way overblown and largely insignificant. I’ve done some stress analysis based on the variation in mechanical properties (anisotropy) with grain direction and it’s not much of a concern. I don’t believe any increased size at the bend is required, but I do this for added safety margin.

Out of thousands and thousands of mainsprings we’ve made, not one has broken to my knowledge.

I would argue the forging process in itself, would introduce opportunity for error and result in a much higher scrap rate. For example overheating material, bending when too cold, thinning of material based on the bending process etc.

Another interesting fact is that all of the fantastic locks Jud Brennan makes have mainsprings cut from the solid and not bent.

I firmly believe the advantage of a formed spring for a mainspring is negligible at best and probably more likely to cause problems.

There he goes again! Clouding the issue with facts, every home hobbyist knows that it’s all black magic to do anything with muzzle loaders!

 

[dave_person]

Hi,
Jim I am not denigrating your springs but as I understand it, you went through a learning period milling your springs such that they did not risk taking a set after a period of use. I am not talking about breaking them, rather losing power over time because the grain of the metal runs straight through the bend as if you cut it from a solid block of wood. You wrote you thickened the metal at the bend as an added safety factor, which is good. But why did you feel you needed to do that as a safety factor? On a forged spring, there is no need to do that. Now the OP needs to make a spring. I would argue it is easier for him to forge a good spring than mill it unless he understands the nuances of milling a spring, which you learned. After all we have centuries experience with forged springs and only a decade or so with milled ones. I focus my comments on understanding the OP's needs and address them.

dave

 

[James Kibler]

The first springs I made took a set because they were too soft. It had nothing to do with grain direction. The only reason a spring takes a set over a relatively short period of time is because the yield strength is exceeded. Grain direction doesn’t have a significant impact on yield strength.

We made springs stronger ( harder) and the problem was solved.

As to making the bend thicker, yes, this is to increase strength at this region. Tensile strength is slightly less perpendicular to grain direction, but not much ( I’ll look up numbers again and post). So why not make a little thicker. This is better than the thinning I see in your example.

Again, the problems that can occur from the forging process far outweigh any benefits.

We haven’t had a spring loose strength in many years. In fact our locks are known for their strong springs and speed.

Believe me now or later. Doesn’t really matter.

 

[James Kibler]

There’s nothing wrong with a properly forged spring, but the same goes for a machined spring. Heat treat them exactly the same and they’ll both work the same.

After the first several months of soft springs (less than 40 HRC), there have been zero issues with them.

Making a properly shaped and good looking spring from the solid is easier than forging. This is why Jud went in this direction early on and he can forge with the best.

 

[FlinterNick]

I use 6150 billets. So far so
Good no issues

I would focus extra hard on your measurements key locations where the lug goes in the screw and the bends. Make a few. As They say practice makes perfect.


https://www.blade6150.com/

 

[The Crisco Kid]

There's no mention of cast springs. Any thoughts on them?

 

[FlinterNick]

There's no mention of cast springs. Any thoughts on them?

Cast springs are fine. But I don’t think opinions on cast Springs have any relevance to the OP question about making a new spring.

 

[The Crisco Kid]

Unless he might want to try to cast one. I guess maybe you didn't think of that possibility.