A tool made from solid carbide used in barrel rifling that is larger than the reamed bore. There are three surfaces to the button tool. The straight cylindrical portion of the tool is the pilot and aligns the tool to the bore. The next portion of the button tool is larger in diameter and it is the portion of the tool that forces the grooves into the barrel. This section is ground to the exact reverse of the finished rifling pattern, i.e., the land on the button produces the groove in the barrel. The last diameter area of the button tool is the bore section of the tool, which passes over the top of the land, smoothing it and maintaining a true round bore. Any toolmarks that are in the barrel before rifling with the button will still be in the barrel after the rifling, although they will be smoothed considerably. Refer to Rifling Methods – Button Rifling.
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