It is often observed that it is very difficult to find a blacksmith who knows how to harden and temper rock drills; but the trouble begins when the smith puts the steel in the fire. Overheating is the cause of all the mischief in tools of highly carbonized steel.
For rock drills, good tool steel must be used. The most common size is five eighths round or octagon steel. The shape should be a cutting edge, with the corners a little rounding, and not, as some prefer, a diamond point, for it is very difficult to harden a diamond shaped rock drill, for the point is liable to be too hard, while the corners are too soft. In hardening, heat to a low red heat, and cool off in water. A little salt in soft water makes a very good hardening fluid for all purposes. Place the drill in the water just deep enough to harden, and leave heat left in the drill to draw the temper. Then take it out of the water, and brighten. Now watch for the temper. When the edge is yellow, cool off. Another method is to heat and place the drill in a trough where there is water only one-half an inch deep, and do not draw the temper, but place it in the water, and let it cool. If the heat is right, this method will give satisfactory results; of course, some will break at the water line.
In our day, we hear much about hardening compounds and welding compounds. An old smith once bought a receipt for a hardening compound, and paid a stiff price for it, and now I shall throw it in free to every reader of Standard Blacksmithing: Aqua, one gallon, Chloride of Sodium, four ounces. The receipt he kept as a great secret, and succeeded remarkably well in all kinds of hardening. He generally bought it in the drug store, and paid a dollar for one gallon of water and four ounces of salt. If this smith had known what a simple fluid he was using, he would have lost faith in it and failed. As it was, he thought it something wonderful and succeeded. The fact is that soft water and a little salt is the best hardening fluid for all edge tools, but we do not like to “call a spade a spade.” I know a physician who prescribed the same thing for all ills, – a four-ounce bottle of chloride of sodium and aqua, – and he had the reputation of being the most wonderful doctor in that part of the country, for 99% of his patients got well. I also believe that it would be a blessing if all physicians would prescribe the same thing in 90% of the cases which come under their practice, for 99% would get well from it. As it is now, many are poisoned; they simply go to sleep, and forget to wake up. I have been so near the grave myself that it was a miracle I was not taken off through the prescription of a lubber doctor. Still, you will buy something you don’t know anything about for a hardening fluid; but if you are sensible, use salt water. Only a handful is enough for two gallons of water.
There are many welding compounds on the market. If you examine them, you will find that they are mostly borax and steel borings, or clay, borax, and steel borings. During the hard times a few years ago, a tramp blacksmith coined not a small sum by selling red clay to his brother smith for welding compound. He dug out twenty-five pounds of red clay in a pit where clay suited to welding iron and steel was plenty; then he put it up in small boxes of about four ounces each, and sold to the smiths for 50 cents per box. Now we have a company organized for the purposes of selling red clay and steel borings to the smiths for welding fluid. It is not a bad compound either, so long as the smith does know what it is, but as soon as he finds out what it is it is “no good.” There is lots of clay that is just as good a welding compound as is wanted, but, by the way, do not forget the sand pit either. Sand, clay, borax, and steel boring, scales of steel or iron, are elements of which the best welding fluid can be made, and, if you fail to make good welds with these ingredients at your disposal, there is something wrong with the man behind the anvil.