Rehash a heat treat question

[CALNNC]

There was a thread about heat treating here a while back, but was not exactly helpful in my case. I have been machining replacement firing pins for my American Arms Silver O/U shotgun for a couple years now, and need to harden the hammer end of them more effectively. I am using either oil hardening or water hardening drill rod to make them. I thought I had a handle on the austenite-marsentite quenching point, but apparently not. I have been hardening the hammer end only. So, need some knowledge about how to do a more effective heat treat on this. Am I using the right steel? Would case hardening be a better choice? I still have some Kasenite in the cupboard for that. Oil, water, or air cooling the best option? The firing pins are stubby little things about an inch long and 1/4 inch diameter, the hammer end has a deep notch in the side, that presents a smaller strike face for the hammer. The hammer is peening this end. I also have issues with the original problem that started this ongoing project, the firing pins break at the taper point between the actual firing pin end to the main body of the pin. The receiver casting was not machined where the pins go, you can see casting roughness in there, including the shoulder the springs rest on, and there is really no way to smooth this area as it is not lined up for any reamer I have to get into the pin holes due being blocked in line by the remainder of the receiver frame. I would have to cut a reamer down to about 1/4 of its length to do that, if anybody thinks cleaning that area up might help to increase pin life. I use this for trap shooting, and it routinely breaks them after about a 1000 rounds, might last forever if I hunted with it and fired maybe a box full of shells every year or so.

American Arms imported these things from somebody in Italy, and it is a well made shotgun whose guts are identical to several higher end models, but they must have cheaped out on the firing pins. Picked this up at a gun show a few years back for a song, but in a month it failed to fire the lower barrel which led to the broken pin discovery. Parts are in the unobtanium category. Why not get another shotgun? I hate to be beat by a problem like this, and if I can solve it, I'll feel better about selling it and maybe then getting another shotgun. As many people that are out there looking for firing pins for these though, maybe start a cottage industry supplying parts. If anybody currently makes these, let me know and save me the trouble.

[Idz]

I gave up on the vague color method of determining temperature as it is so subjective and depends on lighting. I've had great success making reamers from W1 steel by heating them inside a hole in a clay brick using a propane torch. Get a small magnet and heat the piece until it becomes non-magnetic and you're very close to the ideal temperature. Maintain that temperature for about a minute and then quench. I don't temper my reamers and they work great forming perfect curly chips. You probably have to temper firing pins since they have impact loads.
Case hardening is probably even better since you have a very hard surface with a ductile core to handle impacts.
good luck

[Any Cal.]

I have a heat treat oven for some things, but tried to harden 01 drill rod with a torch. Failed badly. I think the O1 requires a longer soak, not just bringing it up to color.

In the small cross section it should quench easily, maybe even enough in air.

Not saying this from experience, but I would try oil hardening over water hardening just because it would be less likely to warp.

You could also try putting oil over water or visa versa to speed or slow the quench, depending on the steel you are using.

[Skipper]

Good article

https://hocktools.wordpress.com/2011/01/31/diy-heat-treatment-of-tool-steel/

[lefty o]

i believe mossbergs silver reserve is the same gun as the american arms.

[W.R.Buchanan]

O1 requires you to soak the part at or slightly above the hardening temp of 1450F usually 1500 works better because the part will never get to 1450 if the temp is set at 1450.

The amount of time you soak the part at temp is 2 hours for every cubic inch of material. IE: a 1" cube needs to soak at 1450+ for 2 hours to completely get all the material hard.

Obviously a firing pin won't need 2 hours. but soaking it for 15 minutes wouldn't be wrong. Then it is dropped into oil to cool it.

A proper material for Firing Pins is generally considered to be S7. and that's what you need to be using as it is impact resistant. If you have a copy of the Machinery Handbook ( which you kind of need if you are doing this type of work ) if gives all the profiles for heat treating just about any kind of material.

Randy

[knifemaker]

The above post is correct for 0-1. Heat to 1475-1500 and soak for 15-20 minutes. Almost impossible to do this with a forge or torch, quench in oil, canola oil can be used, until near room temp. It will be around 62-63 RC in hardness, which is too hard and brittle for a firing pin. After quenching, heat to about 600 degrees and hold for one hour at that temp. Should bring the hardness down to around 51-52RC. If you do not have a kiln where you can temper the firing pin at 600 degrees, there is another solution you can try. Heat some lead in you casting pot to 600-625 degrees and plunge the firing pin into the lead for about 2-3 minutes and that should bring the hardness down. Old English gunsmiths used this methold when making leaf springs for shotguns in the 1800's.

[KenH]

The above post is correct for 0-1. Heat to 1475-1500 and soak for 15-20 minutes. Almost impossible to do this with a forge or torch, quench in oil, canola oil can be used, until near room temp. It will be around 62-63 RC in hardness, which is too hard and brittle for a firing pin. After quenching, heat to about 600 degrees and hold for one hour at that temp. Should bring the hardness down to around 51-52RC. If you do not have a kiln where you can temper the firing pin at 600 degrees, there is another solution you can try. Heat some lead in you casting pot to 600-625 degrees and plunge the firing pin into the lead for about 2-3 minutes and that should bring the hardness down. Old English gunsmiths used this methold when making leaf springs for shotguns in the 1800's.

What KinfeMaker says - just follow the above post.

[knifemaker]

CALNNC, A little more information on heat treating your firing pins. If you do not have access to a electric kiln to heat your firing pins to 1475 degrees, use a torch or forge to heat them to red hot and use a magnet to test when the magnet will not stick to the firing pin. At that point heat for about 15 seconds more then plunge the firing pin into the oil and leave it submerge in the oil for about 2-3 minutes. Remove from oil wire brush any scale off and plunge into the melted lead at 650-700 degrees and leave it submerged for about 2 minutes. Remove from melted lead and allow to air cool. Should be good to use after that process.

[M-Tecs]

The magnet never lies. Very few people use them for heat treating but 100% reliable.

[targetfreak]

Have you ever heard of case-hardening compound? One simply heats up the steel (of almost any composition, tool or not), then plunges it into a can of the hardening compound (a powder) until cool enough to handle. Repeat as often as desired. "Cherry Red" is one brand name.

[knifemaker]

Going from memory from years ago, but I think the old English gunsmiths used "Lime" to do what targetfreak commented on. That compound just may be lime.

[Chill Wills]

Have you ever heard of case-hardening compound? One simply heats up the steel (of almost any composition, tool or not), then plunges it into a can of the hardening compound (a powder) until cool enough to handle. Repeat as often as desired. "Cherry Red" is one brand name.
Kasenit

[targetfreak]

Kasenit

Yes, Kasenit is even better than Cherry Red.
If it was simply lime, that's what tool & die makers would be using.

[375RUGER]

you need to harden the whole pin and then temper it to increase the toughness. You're tooting in the wind trying to harden one end of a part that small.

[David2011]

Going from memory from years ago, but I think the old English gunsmiths used "Lime" to do what targetfreak commented on. That compound just may be lime.

I've put hot parts in lime when annealing or tempering/drawing to make them cool slowly. It keeps air away and acts as an insulator. There's no chemical interactivity that I know of.

[colonelsanders]

make the firing pin from a grade 8 bolt. They are alloy steel (chrome-moly) and already quenched and tempered.

Problemo solved