| 摘要 |
A method for broaching a gain twist rifling in a gun barrel comprises cutting the initial tracking groove in the gun barrel, and thereafter passing a plurality of freely rotatable cutter assemblies disposed in spaced apart communication with each other, so that the cutters projecting from each cutter assembly pass sequentially through and may freely rotate within the tracking groove to successively increase and refine the diameter to form the final rifling grooves. The apparatus comprises a plurality of cutter assemblies mounted in spaced apart position along a support and drive shaft. The cutter assemblies define radially extending cutters, and are arranged in the order of increasing radial extension of the cutters, so that the radialmost extending cutter assembly makes the final pass through the tracking groove to complete the broaching operation. The cutter assemblies are preferably adapted to remain non-rotatable along the shaft until they engage the tracking groove, and the apparatus includes an indexing assembly that aligns the cutters with the tracking groove. The present invention eliminates the need for repeated cutting passes to achieve a uniform gain twist in the rifling grooves.
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