Using modern machines and tools to create those important grooves.
by Charles J. Moore
Because gun barrels have been rifled for so long in so many different regions of the world, the device that is used to guide and support the hook cutter during a rifling operation is known by several different names. These names include, but probably are not limited to, rifling cutter box, rifling cutter head, rifling head, rifling box, rifling bar, and cutter box. As far as I know, there is no one correct name for the tool; all of the preceding names seem to be equally valid. I use the term rifling cutter box simply because that is the first name for the thing with which I became acquainted.
Early rifling cutter boxes were made of hardwood or brass. They were hand fitted to the bore size of the gun barrels to be rifled and were tapered on each end to permit easy entry into the bore. A small slot was cut into them and a hand-made cutter was inserted into the slot. The cutters were made of hardened iron and usually had multiple cutting edges, somewhat like a saw blade. The cutting edges were formed with a triangular file. Because the angles of the file’s corners were 60°, the cutting edges formed in this fashion usually had a negative rake of 30°. With a such a steep negative rake angle, these cutters were incapable of actually cutting material away from the barrel. The cutters could only scrape away fine shavings from the wrought iron barrels. As with the other early tools used to make rifle barrels, these early rifling tools required quite a bit of time and labor to accomplish the task of rifling a barrel. And the cutter boxes had to be replaced after rifling a few barrels, although the ones made of brass tended to fare better than those made of hardwood.
Read more in the December 2015 issue.