Hardening Steel

[R. McAuley 3014V]

When hardening steel gun parts, how do you determine the right instant when to quench the part to obtain maximum hardness? Or is this achieved only through trial and error?

[Eggman]

I heat it with a standard propane torch, sprinkle Kasenite on the critical surface as it gets real hot, then quench it in water when I see the metal begin to glow red. Takes quite a bit of time before you begin to see this. A metals factory guy (Dave Ferguson) taught me this.

[Southron Sr.]

First of all, the CASEHARDENING is only a thin layer of carbon on the surface of steel-that layer is what makes the steel "hard."

HOW I HARDENED A FLINTLOCK FRIZZEN:

I wrapped the frizzen in some old leather shoe laces (making sure that they were REAL leather first!) Then I wrapped everything in a tight ball of aluminum foil, about a dozen layers thick. Then I placed the aluminum foil ball containing the part in my fireplace and build a blazing fire on top of it. As it was winter time, I kept adding logs to the fire until I went to bed.

The next morning I sifted thru the ashes and pulled out the aluminum foil ball. The foil fell away and I had a flintlock frizzen that was a dull gray color. When I installed it on my repop St. Etienne, it sparked wonderfully. It was casehardened.

HOW I "COLOR CASEHARDEN" A REPRO LOCKPLATE:

Polish the lockplate. Lay it on a rock and then sprinkle an ample amount of Kasenit on it. Using a propane torch, heat the lockplate to a red color, playing the flame back and forth across the face of the lockplate. Drop red hot lockplate in can of motor oil. It will come out with beautiful "case colors"!

[Michael Bodner]

Hardening steel is, for us torch and fireplace folks, more art than science. If you have a furnace capable of 1800 degree temperatures (accuratly), you can woek with steel very easily!

But basically, hardening steel is a) bringing the metal to a specific temperature. The cool part of this is that at any particular temperature, the steel will exhibit a particular color. Its getting to understand how to relate the color to a specific temperature range. If it isn't hot enough before quenching, it will be too soft. If its too hard, it will be too brittle. Step b) is to plunge the object into water (or oil) to quickly cool it. This makes the metal hard, but also, brittle. Depending on if it needs some flexability, like a spring, it will need to be tempered, which is basically, reheating it to a much lower temperature than before, and then allowing it to slowly cool. The key word here is slowly.

Use Kasenit allow you to reach higher temperatures than what you can obtain with just a propane (or Mapp) torch. It brings you higher up the temperature/color scale.

Do some Google searches on hardining metal. Look specifically for color/temperature charts. That will get you started.

BTW: The reason a blacksmith shop is often dark, was to allow the Blacksmith to see the glowing metal easier and to distinguish the different subtly colors more easily.

Good luck!!

-Mike

[Eggman]

I should have clarified that all the hardening I've done was to achieve (or reachieve) surface hardness - like the full cock notch on the tumbler after stoning, or the full cock notch on a revolver hammer, same purpose. Frizzen hardening is an art - have watched it done - the hardening (again still using Kasenit), then the drawing out based on color to eliminate brittleness. Old round ballers have seen many a frizzen snap in two when struck by the flint when not done perfectly. Anyway, can't remember what the frizzen was quenched in but it might have been oil. My friend always used a torch.

[Southron Sr.]

Now if you want to harden steel absoutely correctly, Brownells sells an electric furnace in their catalog that cost a bit over $500.00 (the last time I checked.)

[R. McAuley 3014V]

Was just curious what method others were using, and see whether anyone else was using this method:

Magnetic Test for Heat in Hardening Steel

When hardening steel one must know the proper point at which to quench it to obtain the best results. Workmen who do this kind of work regularly, learn to gauge the point of quenching quite accurately, but for the amateur, steel hardening presents many difficulties.

A very simple method by which anyone who wants to harden a few tools may obtain as good results as a professional mechanic, though, perhaps, it will take him a little more time, is by the use of a magnet. The temperature at which steel should be quenched to secure the maximum hardness is just above the point where the carbon in the steel changes from the free to the combined state. Curiously enough, at this same point steel becomes non-magnetic, and by taking advantage of this fact one can harden steel almost perfectly. The ordinary horseshoe magnet is not sensitive enough to show this change, but the balanced magnet illustrated the point is clearly indicated.

Tool steel is preferable for the magnet, but any steel that will harden can be used. A piece of saw steel, or even an old file ground smooth, can be used. Anneal it and then saw and file to shape shown in Fig. 1, and drill a 3/16-inch hole for the pivot, being careful to get the hole perpendicular to the faces. Balance the magnet on a small nail placed through the hole. If it does not balance, take some metal off from the heavier end until it hangs exactly horizontal. If possible, grind the faces parallel and finish it all over. Harden by heating it to a medium red and then quench in water. The metal should be polished, as it movements may then be seen much better in the dim light of the forge. Magnetize the steel by touching it to one of the field poles of a running motor or generator, or wind several hundred turns of fine wire around it, and pass a direct current through the coil thus formed. Only a moderate degree of magnetization is necessary.

Make the support of brass, ½ inch square. Round up one end and square the other as shown in Fig. 2. Drill holes with 5/32-inch drill and then cut the slot. Tap the holes for a machine screw and ream or drill out the hole on one side of the slot to 3/16-inch. Make a headless screw of 3/16-inch brass rod, as shown in Fig. 3, setting a thread on one end and slotting the other with a hacksaw. Leave it a little more than ½-inch long, so that if can be filed up flush with the hanger with in place. Assemble these three parts as shown in Fig. 4 and see that the magnet is free to swing easily through it entire arc.

A piece of 3/16-inch iron rod, 18-inches long, is used for a handle. Threads are cut one end so that it can be screwed into the upper part of the hanger. An old file handle is driven onto the other end of the rod.

The work is heated to a dull red and the point A of the magnet, held by the handle, is applied to the heated part. If a chisel is to be hardened, it must, of course, be tested near the cutting edge where it is to be the hardest. If the magnet sticks to the work, heat a little more and try again. When the work gets to a medium red, it will be found that there is no attraction for the magnet. This means that the hardening point has been reached and passed a little, so the work should immediately be plunged into brine, water or oil, according to the degree of hardness required. If the steel is chipped a little, it will be found to have a very fine grain and is therefore very hard. This method, while not speedy, will produce good results, if care is taken to watch the actions of the magnet.

[Popular Mechanics Magazine, Vol. 18, No. 4 (October 1912), “Shop Notes,” pp602-03.]

[John Wells 3rd US]

Kit Ravenshear was a fantastic gunsmith for antique firearms. His pamphlets are a goldmine of techniques and ideas on recreation, repair, and restoration of classic weapons. Here's a link to his homepage, I guess maintained by his widow or daughter. the pamphlets are still available. There's a good one on metal treatment. Dixie, Dixon's, and others have them.

http://www.kitravenshear.com/

[firelock]

When in doubt about what alloy of steel you are working with, heat to cherry red , quench in oil. Test with a old file ,if hard the file will skate not cut. If the part is not hard then reheat and quench in brine. Brine is a more violent quench and can crack steels meant to be oil quenched. Then you need to polish the part and temper by heating the part till it comes to a particular color. Home heat treatment is almost as much art as science. Trial and error is as good a teacher as any as long as you quench in oil first. If oil does not work then quench in brine. Make sure you heat the steel to the non magnetic point pluss a bit brighter color. If the part still does not harden then it must be case hardened using casenite or pack hardening with leather scraps,bonemeal and ground charcoal. Quench in oil. Ther's more to it than this three cent overview but it is easily learned from a veriety of sources.

[John Wells 3rd US]

When drawing temper, the heat has to be applied VERY slowly, as the polished part moves through the color changes rather quickly. There's a product called Tempi-lac which is like a paint that is applied to the part if you're uncertain about this. available in several temperature ranges, it essentially melts at the temp desired for the part being tempered. I think Brownell's used to carry it, no doubt other sources as well.