To Fit a Hammer on a Tumbler.—To file the hole in a gun-hammer so that it will rest firmly and evenly upon the squared end of the tumbler, has tested the skill and patience of nearly every gunsmith. The usual practice is to drill a hole nearly the diameter of the square of the tumbler, then file this hole until it fits the square, and unless skill and patience are brought into requisition, and a nice fit be the result, the hammer soon works loose, then needs refitting. The remedy then generally is, remove the hammer from the tumbler and close the hole a little by cutting around the squared opening, a little distance back from the edge, with a sharp cold chisel, thus throwing some of the metal inward, closing the hole a trifle. The hammer is then put upon the tumbler, and if it be a little tight is driven to place with a hammer. After some usage it becomes loose again, and has to be again refitted.

It is evident that unless what might be called a “perfect fit” be made, that the sudden arrest of the hammer upon the tube or cone, as it descends by force of the mainspring, will cause some slight displacement of metal where the hammer and tumbler come in juxtaposition. A repetition of these sudden arrests increases the displacement, and often there is considerable looseness of the parts.

The Drift for Squaring the Hole.—The remedy for this is very simple, and can be performed with but little labor. After the hole in the hammer is drilled introduce the end of a square drift, and drive it steadily through with blows of a hammer. The drift will cut a clean hole, the exact counterpart of its form, and this hole will need no finishing, if the drift be properly made to insure its correctness as to being smooth and true. Bear in mind that while driving the drift, the work must rest evenly and solidly upon some firm support, but in such a way that the tool will easily pass through. The drift is shown in Fig. 48. In construction it is a rod of steel filed or so shaped that its transverse section is of the precise form that the hole is to be made, and too great care cannot be taken to insure its being as correct as possible. The entering end of the tool should be made round, and almost fill the hole as drilled in the hammer, and it should increase gradually in size until it arrives at the full proportions and then gradually decrease to the upper end, so that it will readily pass through the opening made by the larger portion. On the sides of this tool are cut teeth that extend around it, being continued from side to side after the manner of a screw thread upon a bolt. It will be observed by reference to the cut that the teeth commence on each side of the square and resemble a four-threaded screw, with saw-shaped teeth, made upon a square rod. A file is the most ready tool to cut these teeth. Forge the steel carefully, temper equally, and do not leave too hard. When properly made it will last for an untold amount of work.

The number of cuts or teeth to the inch may be about ten. There must be sufficient depth between the teeth to receive the cuttings, and they must be made strong enough to withstand the hammer blows. In driving use oil on the teeth, and be careful to keep it upright, so as to form a hole that will enable the gun-hammer to stand properly on the tumbler.

If it be feared that there will be a variation of the hole from the “square,” turn the drift a quarter turn after the first driving and drive again; then turn another quarter and drive the third time, and so on of the fourth.

The drift may be made of almost any shape, and will produce holes of irregular form as readily as square ones. Another example is the mortice in the loop attached under gun-barrels, through which the bolt passes, and also the same size mortice or slot in escutcheons, which are let into the stock, through which the same bolt passes. The holes in small solid wrenches to receive square or six-sided nuts can be readily and easily made in the same manner.

A Tool for Fitting Hammers to Gun Locks.—The usual practice in fitting hammers to gun locks is to measure with the dividers the distance from the centre of the tumbler, where it projects beyond the lock-plate, to the centre of the tube or cone, and so get the length of the hammer; then drill the hole in the hammer, square this hole by the rule of “guess,” and file until it fits upon the square of the tumbler.

A simple tool can be made by any gunsmith, that will greatly facilitate his operations in fitting hammers. The accompanying cut (Fig. 49) shows this tool in full size. It is made of iron or steel, one-eighth of an inch thick. The body, A, of the tool is one-half inch wide, and has a slot, a, three-sixteenths of an inch wide and one inch long. The curved slot, b, is the same width, and embraces about one-fourth of a circle. The nose-piece, B, is shaped like the top portion of a hammer, and is held to the body, A, by a screw, c, and to insure its moving in a line, and being held properly in the slot, a, there is a small stud, d, that fills the slot. In the lower curved portion of the body, which is seven-eighths of an inch in diameter, there is a five-eighths hole, which receives the round portion of the piece, C. This piece has an extension, as shown by the dotted lines, and is held to A by a screw, e. The square hole in this piece is intended to fit the square of the tumbler of the lock. The thickness of C, at the round part where it enters A, is the thickness of both A and B. There is a shoulder of the thickness of B, and of the size of the body of the tool at the lower end, being of the same diameter, so that the back surfaces of B and C are of the same thickness. The front surface of C is flush with A.

To use the tool, put the square of the lock tumbler in the square hole of C, and put the tumbler screw in place. Loosen the screw, e, and turn the piece, C, until the nose of B will rest pretty firmly on the gun-tube; then turn the screw to hold it in place. Loosen the screw, c, that holds B in place, and move this piece up or down until the centre of the nose rests squarely on the tube; then confine it in place by turning up the screw, c. This is now an exact pattern, giving the length, shape of the hammer, and also a guide to form the square where it fits the tumbler.

It must be observed that the screws and the stud, d, ought to fill the slots on the shoulder of the piece, C, a good fit, so that it will turn evenly and properly in the hole of A. The screws may be the same that are used for tumbler screws for army muskets. These screws are hardened, and, as they have large flat heads, they answer for this purpose very well.

The part, C, can be made of two pieces of the same thickness as the other parts. Finish them separately, except the square hole, and then solder or rivet them together. The square hole is best finished up when the two parts are fastened together.