Mechanical Hints (Making Patched Bullet Molds)
American Rifleman, vol 30, No. 15, 25 July 1901, page 290.
The general principle of this tool is like a common, flat chuck drill, with a hog-nose end and rounded instead of angular cutting lips. As it is to be used on brass, heat it to a cherry red, and harden, in clear, soft water. Leave it hard, and do not temper. Then grind it lengthwise on a fine grit stone until the size and shape are right, testing with the micrometer, on the cutting edges until the exact dimensions are found at the larger part, which is to form the bullet at the base. It is not necessary to taper the cutter forward of the base mark—which is made with a sharp cornered file before the reamer is hardened—but care should be used to prevent the blade from cutting any wider forward. When ground very nearly to size, hone down from the top of cutting edge to narrow; or, to use a common phrase, back off from the front. That leaves a scraping edge, which, if nice and smooth, will leave a very fine polished surface inside the mold. Make the distance across the corners the exact measurement you wish the bullet when finished. As a matter of course the reamer must cut a shade larger than itself. When heated, the brass will expand, but the bullet will shrink in cooling, so the size will be found about right, or so nearly so that by using a little thicker or thinner patch paper the results are reached.
Having the reamer made, which should not require one-quarter the work necessary to make a fluted cherry, select a piece of oblong, soft steel large enough for the length of the bullet to be made. Through it drill a hole large enough for the brass rod, in which the mold propel is to be cut. This for a .32 caliber may require a rod of brass 9-16 inch in diameter, and length to fill the hole in oblong steel piece, say 1 ½ by 7/8 inch, or it may be heavier to retain the heat and keep the mold at a more even temperature when casting. For a shank or handle, the bar may be forged down or a hole may be drilled in the end and a piece of steel rod pinned in, to which the wooden handle is attached.
The brass rod is next fitted into the steel and a hole drilled through all, at the bottom, below the point of bullet, to prevent the brass coming out when hot. With a small piece of steel rod pin firmly in place. The whole is then firmly strapped on the face plate of the lathe. Of course the work has been got out square and true so the piece of brass rod will run in line. Then with a graver, over the T rest spot the center, true, large enough to allow the end of reamer to enter. Then rig the drill rest and with the dead center of lathe in center spot of reamer drill the mold down to the bottom, which will be shown by the file mark on the reamer. Do not force or hurry the work. Draw back often and clear the chips. Keep the work wet with water, instead of oil, and go slowly at the finish, when you should have a nicely cut mold at a slight outlay of time and money.
If one wishes a double mold a good way is to drill two holes in the steel near together and fit two pieces of brass rod. In so doing, however, I have found it best, after pinning the brasses, to remove them, then drill them in a common three-jawed chuck as before directed; then pin in place and strap the whole on the face plate, to square up and smooth. But, if nicely done, as the work progresses the brasses will be all right when bored. Across the top of brasses, at base of bullet, make eight or ten sharp file marks, to give the hot lead vent; let the marks run in all the different meridians.
[ed. note this venting on the top of the mold halves...]
Next fit the cut off. The sprew hole should not be too large. The countersink should leave the edges sharp to cut off the sprew clean and easily. The knock off should project at the end rather than at the sides. One screw should be sufficient for a single mold, but for the double mold I prefer a slot in the cut off made on the arc of a circle, and two screws. See that the threads are well cut, full and sharp, and drive tight enough to prevent working loose in use.
Some gunsmiths make a half round reamer by turning a piece of steel just the size and shape of the bullet and filing it off longitudinally, one-half, using the micrometer, then hardening and honing the edge sharp, and grinding the point like a cannon drill; but I like the flat one best, as it clears much better and can be made over for a smaller bullet if desired. This same flat reamer is what was used for making the old muzzleloading swages, working them out nearly to size first, then finishing with the flat reamer and oil, with a splint of soft pine on each side. The smoothest and best finished swages I ever saw were cut with such a tool. It is not a rapid cutting reamer, but leaves the work nicely finished.
A mold made like the one described not only does nice work, but has the advantage of being quickly and easily changed or made over, as the humor may take one. And where is the genuine rifle enthusiast who might not wish to experiment with this mold, to perhaps make a dozen different bullets of different lengths and shapes? That he could easily do by making other reamers and new brasses for his mold.
A good, large wood handle is not only more comfortable to the hand, but gives a better grip and is less liable to get loose by burning. It is well to form the shank of the mold so that new handles may be easily put on. A square shank driven in a round hole, with a small pin through the whole is good, and can be easily replaced if worn or burned. Bullets with sharp or rounded points may be made with the flat reamer, but it is necessary to thin the reamer at the extreme point so the edges can cut clear to the end.
For grooved bullets a split mold must be used, to make which a cherry must be filed, and finished to close the mold on after the body has been cut out. For a grooved bullet I prefer an iron mold, but form a smooth, patched bullet the brass or composition lined mold is preferred as giving more uniform results. There are nice molds in the market, but if one wishes a special, for experimental purposes, he may find it not only difficult to obtain but expensive withal and unsatisfactory in the end. If one can make it himself, and the results are not what he wishes, or expects, he may easily change it so the next one will be better.
If the mechanic who is to make the mold described above is handy at tool making I would suggest that he make a reamer or drill a trifle smaller than the finishing cutter and run in first, thus leaving the hole a trifle small in its diameter, and a little shallow. Then finish carefully with the second cutter, keeping the brass well wet to prevent heating or chattering. Brass may be run at a lively speed when cutting, but care should be used not to crowd the feed. If the sportsman does not wish to make two cutters or reamers he may run a small chuck drill down part way to the bottom of mold to remove some of the stock, but the beginner will probably do best to use one cutter only, and making the work come out surely, even though he goes slowly. I have made many such molds and never saw better looking bullets than came from them.
H.