Rifling a Gun Barrel
The rifling machine, in its most approved form, consists of a bed carrying a head for holding and indexing the barrel, and a carriage having a spindle for holding the rifling rod, and all the appliances necessary to control its motion and feed the cutters automatically.
The head has a spindle which holds the barrel by means of a convenient chuck, and is provided with an indexing arrangement by which it is automatically turned at the end of each stroke of the rifling rod through the proper angle to give the required number of grooves.
The carriage has a spindle for holding the rifling rod, on which is a pinion meshing with a rack on the carriage cross-slide. The carriage is given a reciprocating motion by means of an ordinary open and crossed belt-reversing mechanism, which is operated by dogs on the carriage at the end of its stroke. The rifling bar controls the twist of the rifling, and is placed above the carriage, and connected with the carriage cross-slide by means of a swiveled slide. It is pivoted at its central point so it can be set at any angle, and as the carriage moves along the bed a transverse motion is imparted to the carriage cross-slide. This causes the spindle to turn as it advances, so that the rifling cutter describes a true helix. If an increasing twist is required, the rifling bar must be formed to suit the curve of the rifling, the ordinates of the curve of the rifling bar being in the same proportion to the ordinates of the developed curve of the rifling as the pitch diameter of the spindle pinion is to the bore of the gun.
The rifling rod is provided with one or more cutters, which are fed out by means of a wedge-shaped plunger, which extends beyond the end of the rod, and is driven in at the end of the stroke by an automatic feeding device. This is arranged so that the feed is always alike, whatever the variation in the travel of the carriage, and stops when the cutter has reached the proper depth. The rifling bar being set at the proper angle, and all the dogs and stop nuts being adjusted, the barrel is placed in the head, and the machine started by a lever placed at a point on the bed where the operator can observe all the motions of the machine. After starting, the carriage continues its reciprocating motion, the head indexes the barrel at the end of each stroke, and the cutters are fed until the grooves have reached the proper depth, when the feed stops, the machine is stopped by the operator, and a fresh barrel is put in place.
This machine is designed to take gun barrels of any size up to forty-five caliber and thirty-six inches long. The regular machine is arranged for four, five and six grooves of uniform twist, from straight to one turn in five inches, either right or left hand, but can be built for any number of grooves, and for an increasing twist of any desired curve. The cutting speed for ordinary steel is thirty feet per minute, and is uniform throughout the stroke. The larger machines differ somewhat from this machine; the indexing arrangement being operated by hand,
Farrow, Edward S. American Small Arms; a Veritable Encyclopedia of Knowledge for Sportsmen and Military Men. New York: Bradford, 1904. Print.
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