_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.