Spring Steel

[JGMC]

I'm considering trying to build my next lock from scratch. A simple early style snapping matchlock seems like a good beginners project. I've found a number of good examples of early 16th century pieces to go off of.

I've been reading up on here about how to harden and temper springs. But how do I choose what of spring steel to start with?

How is spring steel graded? What is the best kind for making gun springs? I don't know much about steel at all, so you might have to dumb it down a little for me :redface: .

Also, where can I acquire steel for springs?

- Joey

 

[jerrywh]

Brownells sells spring steel. http://www.brownells.com/.aspx/pid=390/Product/EXTRA_WIDE_SPRING_STEEL

 

[JGMC]

Thank you!

Now, how I determine what size I need? I imagine that more thickness equals more potential energy. Is there an equation I can use to determine the strength by size?

 

[ohio ramrod]

Dixie sells blank spring stock that will temper nicely in a melton lead bath! :hmm:

 

[crockett]

If I understand your question- it is whether there is a different alloy of mix of materials that creates a steel used for springs. Hence "spring steel". That could be- I'm not sure.
From my experience any steel with enough carbon to be tempered can be tempered to a spring type finish. I have one book on making folding knives- I think the steel was 154CM (?) that was used both for the blade and the spring. I have used various types of tool grade steel that I tempered into springs. I think the biggest concern is there is a sort of flow or grain (like wood) to some steel- or so I've read (DGW catalog) and you should not form a spring that flexes across the grain- it should flex lengthwise with the grain.
Some of this I've never gotten a good answer to so maybe some spring-experts can chime in. In any event I've made such springs as mentioned that seem to work fine. You can even make springs out of brass or bronze- I have a sidelock folder with such a spring.

 

[LRB]

Most common carbon spring steels are of the 10XX steels, from 1075 to 1095. Your target range of hardness is the mid to upper 40's in Rc hardness. To get there can be a guessing game, but if oil quenched, most often a lead bath will give you a decent spring temper, but run it at a high temp. 750° to 800° if possible. A good enough range, although I have in the past gotten decent springs at the melting temp of lead at 625°with 1095 steel, although that is lower than recommended, and those may yet come back to haunt me. Here is some info from the late John Bivins on spring making.
http://www.lrml.org/technical/gunsmithing/heattreatml.pdf
Many do not realize that temper heats depend on the hardness aquired with the quench process. 1095 only reaches full hardness when brine quenched, and most tables reflect their temper heats accordingly. If oil quench you would need to lower the recommended heat to temper. V springs require more attention in the temper than plain straight, or bent springs. Always bend spring stock at a red heat. Never cold.

 

[Zonie]

I agree with crockett's thoughts about the grain direction and as a point of reference normally when flat spring steel is bought the grain direction is the same as the long direction of the stock.

The various spring materials have varying resistance to breakage and work hardening in various environments but the 1075-1095 steels Wick mentions are probably the most common and will work quite well if they are tempered correctly.
Proper tempering is perhaps the most important thing for a good spring life.

Speaking of steel and hardness and tempering something to keep in mind is that there are NO spring steels that resist bending much more than another type of spring steel. Yes, there are some slight differences but for the most part they can be ignored.

The Modulus of Elasticity which is a measure of the resistance to bending of a material is nearly the same for all steels from the simple carbon steels to the advanced high alloy steels.
For those with a need to know this value in tension is very close to 28,500,000 to 30,000,000. Usually 29,000,000 is used.

This number is used when calculating the amount of deflection of a spring when subjected to a given force. By using 29,000,000 the answer will be within 3 percent of being correct.

I mention this because some folks get the idea that by getting some sort of "special" high priced "spring steel" they will end up with a "more powerful" spring. For most applications the small differences are not worth the money unless the spring is going to live in a harsh environment like a furnace or an acid bath.

 

[Vaino]

I've made a few springs from 1095 spring steel and for hardening, heat to a slight orange red and quench in motor oil. Polish and temper by laying the spring on a 1/4" thick steel plate using a torch from underneath or submerge in lead or better yet, use a controlled temp furnace. The desired color is a blue gray and the bends especially have to be heated to this color. To avoid breakage, the spring length has to be w/ the grain, all transverse file marks must be polished out, the edges can't have any "marks" or nicks and a slight radius is filed and polished on all corners. These "marks" are stress points and breakage will likely occur at these "marks". Also a radius at all bends in lieu of a sharp corner eliminates stress points. I've seen 1095 sheet spring steel in various thicknesses available at some MLer suppliers. I've also made mainsprings from a solid block of tool steel that held up well, but it's a lot of work. Asre spring force, comparison of thicknesses of existing springs and their applications should give some idea of the needed force. Much time and effort goes into spring making and all is for naught if the hardening and tempering is incorrect or the spring has mechanical flaws. good luck....Fred

 

[JGMC]

Thank you all for the great advice! I think I should be able to conquer the two springs for this lock now. :wink: Or at least give it a good try.