Proper Heat Treatment
Also we all need to keep in mind, as some still shoot original guns, while the Italian replicas are all made of modern steel, the arms produced even of steel during the first half of the nineteenth century only contained about 1% to 2% carbon. Though some arms manufacturers produced guns with steel barrels or even receivers made for cast steel, he first U.S. martial arm produced entirely of steel was the Model 1873 but it was only after World War I that the federal government was able to property heat treat metal without rendering it too brittle. But even with modern steel, many machinists use modern chemical hardeners to treat steel, often rendering it too hard and brittle.
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.
Here is a link to the method your gunsmith may have used:
[Popular Mechanics Magazine, Vol. 18, No. 4 (October 1912), “Shop Notes,” entitled “Magnetic Test for Heat in Hardening Steel”, pp602-03.]
http://books.google.com/books?id=A94...page&q&f=false
First Cousin (7 times removed) to Brigadier General Stand Watie (1806-1871), CSA
1st Cherokee Mounted Rifles | Principal Chief of the Cherokee Nation 1862-66
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