doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Tips on hardening a firing pin.

One must have an idea of the type of steel to determine proper hardening and tempering techniques and heating temperatures. Drill rod could be water or oil hardneing steel, and should be hardened and then drawn, or tempered.
Case hardening drill rod will almost assure breakage.
Extreme warpage almost for sure means too hot a quench.
Unhardened pins may work fine on the primer end but may mushroom on the tumbler end, I've seen it more than once.
Jack would surely have knowledge of the steel of pins he supplied, and of the proper techniques of heat treating. You've be way better off asking him.

Hagen,

I would use kasenit and follow their directions.

You can only harden the pins if the steel is made to be hardened. Some is air, some water and then oil. If you take water hardening tool steel, oil will not do anything to it, except maybe crack it.
Heating just the tip to cherry red is hard to do and the heat will travel through out the part.

Sorry about posting this, I was typing this and didn't see the previous post.

Air vs oil vs water quenching is based upon the "Suddenness" of the quench. Water quenching an oil hardening piece is much more prone to "Cracking" than the other way around. Oil quenching a water hardening part will normally just result in a part not being properly hardened. "Kasenit" along with other carburizing/case-hardening process are designed for steels with a carbon content too low for normal quench & temper processes. This method is designed to put a "Very Hard" skin over a soft core. If you use a through hardening piece of steel & do not tamper it back to correct hardness you have a very brittle part, if you do you just lost the advantage of the case.

Well, you are pretty close, Hagen. Pretty much heat the whole pin to cherry red and quench in oil (or water). Water may be appropriate due to the small size of the pin. No need to quench after tempering. I'd go to blue on the temper color for bit more toughness. It depends on the actual alloy for the exact details; your plan is close enough.

Thanks fellas this forum rarely disappoints.

If I were You I'd be way confused. You got myriad of opinions mostly from men with nada background in metalurgy. Those suggesting kasenit for modern hardening steels and drill rod are way off. Man said to harden the pin after getting length set. He should be able to tell you details to harden it. Almost all modern parts are made of air hardening steel with heat treat oven and pyrometer to hold temp for time specified for hardness required for the application. Do it right by getting details and taking the pin to a shop with ht oven. You going to be an alchemist or do it right?

You will need to find out what kind of steel you have in order to know how to harden. If you are unable to determine the steel composition, this will work in MOST cases. First, forget the colour test. One mans "cherry red" is another mans "bright orange". IMO it takes alot of experience to harden by colour. Instead, heat it to critical heat. This is the temp where the part is no longer magnetic. Put a propane torch in a vice so you can control the part with one hand and a magnet in the other. As the part gets red, touch the magnet to it. If it sticks, pull the magnet off and continue heating. As soon as the magnet no longer sticks when you touch it, quench the part. If it's undetermined whether the steel is oil or water hardening, use a pail of room temp water with 1/8 - 1/4 inch of ATF on top. The ATF will reduce the shock that will crack oil hardening steel and the water will quench fast enough for water hardening steel. If it's air hardening.....????? I dunno. To check for hardness just run a good sharp file across it. If it hardened properly, the file will just skate across it without marking it. It will be too britle to use like this so it will need to be tempered. I would temper it like a spring which is IIRC about 650 deg. Easiest way to do that is to use a lead bath. Put some lead in a melting pot (pure lead ONLY) and put the part on top. When the lead melts, push the part into the lead (it will want to float) and remove from the heat. Let the lead cool with the part submerged. Then re-heat the lead until it melts again and take the part out and allow to cool and your done. Oh, before putting the part in the lead, soot it over a kerosene lamp of candle. The soot will prevent the lead from sticking to the part.

I agree with Cody that using a magnet to determine critical temperature is a good alternative to knowing heat colors. Except for exotic alloys, which are unlikely to be encountered in typical home gunsmithing, the generic heat treat for plain medium and high carbon steel should work just fine. If you don't know the alloy, you can quench in oil. If the part isn't hard enough, reheat and quench in water. You are unlikely to crack a small part like a firing pin; warp, maybe. If you are willing to experiment and learn, heat treating is a relatively easy process.

I agree with Cody on using a molten lead bath for tempering. However, it is not necessary to allow the pin to cool in the lead and reheat. Temper is established immediately by the maximum temperature to which the part is reheated; future reheat above the current temper (exchange hardness for toughness) will further temper the part. Quenching has no effect on temper. You can dunk the part in oil, water, brine, or just air cool it - no difference. The pins from Jack R should also include JR's recommendation for heat treat.

Air hardening alloys literally quench in air. I'm not aware of the use of air hardening alloys in gun work.

There are color charts on the net to compare your part to in both hardening and for drawing it back.
I do agree that controlled heat is the best way, but in small parts a torch, propane or map gas will do it and has done it.

The firing pins on L.C. Smiths were chrome vanadium and an alternate material was SAE 1050-1055.