An end mill is a multi-flute cutting tool for milling machines or routers, used to cut, slot, and profile metal or polymer with flat or radiused tips. In firearm DIY, it’s used to finish 80% receivers/frames by machining the fire-control pocket and trigger slot. Works with router jigs, compact routers or mills, 80% AR-15/AR-10 lowers, and 80% Glock/1911 frames, plus aluminum or polymer workpieces. Available in HSS or carbide; common sizes include 1/4″, 5/16″, and 3/8″.
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