Figure 40.
For larger bores than a forty-four, the tools may be advantageously made a little different, as shown in [Fig. 40]. The shank of the tool may be made of a cheaper grade of steel and the extension much smaller than the bore of the gun. At a, is shown a steel thimble that is turned to the proper size and has teeth cut on the end. This is tempered and is put on over the extension and held by a wire or pin passing through both thimble and extension. At b is another thimble, made preferably of brass, that fits the bore. It can then be worked in the barrel with less fear of scratching the barrel, as might be the case if it were of steel or iron. The space left between the brass thimble and the teeth forms a recess to receive the cuttings. The diameter of a twelve gauge chambering tool will be about forty-nine sixty-fourths, and the diameter of the chambering tool will be about twenty-seven thirty-seconds. The length of the cutting thimbles can be about one inch. The brass thimbles about three-quarters of an inch. The cutting thimbles should rest against a shoulder, as at c. These thimbles should be fastened, a finish turned on the shanks on which they are to remain, after the shanks are turned. The brass thimbles are held by being driven on the extension, and should be turned up true after being driven in place.
When making these tools, form the cutter for the chamber about one-hundredth of an inch larger than the bore of the cartridge to allow for easy extraction. The brass thimbles ought to be of the size of the interior of the cartridge, which is supposed to be exactly the same as the bore. The tool for recessing the head may be a trifle larger, say about a thirty-second, than the diameter of the cartridge head. If it be made one-sixteenth larger it will not matter. Eight cutting teeth are enough for these tools.
CHAPTER XIX.
ON GUN RIBS.
How to Straighten a Gun Rib.—Gun ribs, as received from the manufacturer or dealer, are more or less crooked and winding and must be made straight before being fastened to the gun barrel. Sometimes this straightening can be done with the hands alone, by bending and twisting the rib. If there are short crooks, the hammer must be used. Select a hammer that has a flat pene and this pene must be “across” or at right angles to the handle. See that the pene is not too sharp, but smooth and rounded at its edge. Place the rib to be straightened on a piece of hard wood plank, or what is better, get a piece of two-inch plank about a foot wide and long enough to reach from the floor to a height a little above the work-bench, say about the height of the top of the vise. It may be held in an upright position by means of a screw passing through it into the bench, or it can be so held by setting it on the floor and clamping one side between the jaws of the vise. On this hold the rib, lengthwise with the end of the plank, and using the pene of the hammer, strike blows on the inner or curved side of the rib. Do not strike hard enough to dent or bruise the rib so as to show on the opposite side. By a little practice a rib can be made very straight and true.
How to Fit a Rib.—Sometimes one side of a rib is longer than the other. Fit it into a properly shaped groove in a piece of board, clamp it so as to hold firmly and file away the longer side so as to match the narrow one. The clamps can be made of two pieces of wood placed on each side of the part to be filed, holding them and the rib with wood screws, the rib being moved along as a portion is filed.
How to Fit a Rib to an Octagon Barrel.—To fit a rib to an octagon barrel, file the portion where it comes in contact, square across so as to have all the surface possible to touch the barrel. To fit it to a round barrel, file lengthwise with a half-round file, and so file that the outer edges will fit close, leaving the inner edges a little open, or not quite touching the barrel. A half-round file for fitting ribs to round barrels should have the tang bent toward the flat side so that when the file handle is put on, it will not interfere with filing.