A lot has been said about hardening iron in a charcoal pack and how to go about it. I have done a lot of pack hardening and it is an easy process. To make charcoal , I use an empty cleaned one quart paint can, filled with whatever I decide to char. I have used scraps from powder horns, horse hoof parings, bones, peach pits and old leather belting. I usually char one substance at a time and experiment with different mixtures after the charcoal is ground up. Whatever you use, stuff it into the can and pound the lid on tight. Take an ice pick and poke a touch hoe into the lid, then put the can into a hot fire. I make charcoal in the winter inside a wood stove and all of the funny smells go up the chimney. You can bake the can off to the side of the fire, but right in the hottest part of the fire is best. If you look into the stove you should see yellowish smoke shooting out of the touch hole, that’s good. Leave everything alone until it stops smoking and then knock the can out of the fire to a cooler part of the stove or take it right out to cool. After the can has cooled off you can open it and see what’s inside. It should look just like it did when you put it in except that everything will be decidedly black. Dump everything out into a pan or a sturdy box. you can now easily crush the charcoal into a coarse powder and use it for your pack hardening projects. I usually mix in some crushed egg shells and maybe a little salt for an accelerant. There is quite a bit of science behind the process of hardening and although I have read and reread many metallurgy documents and have understood them, I always shake my head and go to what I know what works. I just like the voodoo version better.
Pack Hardening is extremely useful in lock making and set trigger making. We could argue that we could simply make all of our parts out of some kind of high carbon steel and if you are machining parts, that might be the way to go. Modern casting techniques have provided us with really nice locks, but in the early 19th century and before, something on the order of 100% of gun locks were hand forged. Some swages were probably used as swages are used in every blacksmith shop. The simple truth about high carbon steels is that they are used because of the hardness. That hardness does not go away, entirely at red heat which makes for hard hammering. Coupled with the fact that high carbon steels do not like elevated temperatures, tells me that the old time smiths used wrought iron for all of the gun parts. (except for the springs)
To use the charcoal that you just made, we will need a steel or iron box with a lid. for the following experiment I made some very crude boxes out of thin wall square tubing and some scrap steel. All of this material is slightly less than 1/16th inch thick and the life span is very limited. Each box received a layer of charcoal about 3/8 of an inch deep.
The iron test pieces were laid on the charcoal and the boxes were then filled up with more charcoal and the lids put on. No special effort was made to seal the boxes up, they were simply loaded into a propane forge and warmed up to about 1500 degrees. I usually heat boxes up in a coal forge, but I wanted to do three boxes with different charcoal bases to see if one might be better. I used bone-antler based in one, peach pits in one and leather in the third. I did not use wood char because it seemed too pedestrian and like I said before, I like the voodoo aspect of it. Btw each of the iron pieces were cut from the same bar and the flat faces were ground to free the surface from scale. The three boxes were heated for about an hour and a half and once they were hot I throttled the gas back so the forge was cooking along with a minimum of fuel. A lot of people like to dump the whole box into the quench at once, but I prefer to remove each piece and quench them individually. After forging and filing and fitting a whole flint lock, it seems crude to treat all the parts like a basket of potatoes. I want each piece to hit the water the way I want and I really don’t want to fish around in the bottom of the slack tub for little parts.
The test pieces were removed from the boxes one at a time and immediately moved to a cold water quench with a small pair of tongs. For these pieces I did not draw any tempers, because I wanted them to break cleanly. After drying them off, each piece was supported by 1/8 inch thick steps of steel and then broken by a hammer driven fuller. One whack from a two pound hammer neatly snapped each piece in half, to reveal the end grain of the metal.
As you can see, the carbon combined with the iron to a considerable depth, (in exess of .030”). With the three different chars, I did not notice any variation in surface appearance or case depth. Spark testing was quite uniform. I have no idea what the brinell hardness values might be, but this piece of metal will dent my very best cold chisels. It isn’t too difficult to understand that the carbon has actually COMBINED with the metal and that iron does not have “pores” that the carbon climbs into.
Given the relative ease of forging lock parts from wrought iron and knowing that the parts can be so easily carburized, I can imagine that most frizzens and indeed most lock parts were always made from iron. On heavily used guns, half soleing is a very effective repair. Later locks with V pans may have been made with steel soles from the get go and it makes sense that these frizzen faces were intentionally prominent and were made from Cast Steel as a marketing scheme. Nothing wrong with it, but not nessesarily any better. My last comment on frizzen faces is that after forty plus years as a blacksmith, I would consider forge welding a steel face onto a frizzen to be a ridiculous idea. Really high temperatures which affect grain growth, which affect the quality of the steel can be rectified but bending the frizzen and hammering the foot from a bi-metal laminate is just much to much work, with unpredictable results.
I would love to hear comments , questions and how other’s experience compares or differs to what I have tried to illustrate here.
Clint Wright
