hog
To take a rough cut, quickly removing material; to hog out.
hog: aggressive roughing that trades finish for speed
To hog means to remove material quickly and in large chips, prioritizing stock removal over surface quality. In machining, hogging is the first aggressive pass after setup, when a cutter pushes hard into the blank to clear away bulk material before finishing passes refine the geometry. The cutter feeds fast and cuts deep; the resulting surface is rough, the tool load is heavy, and the sound is loud.
Hogging works best on rigid machines and rigid workholding. A part clamped in a vise or chuck can tolerate the forces that hogging generates. A thin wall or part held by soft fingers will chatter and break tools. The material being hogged matters too: soft aluminum and brass hog easily and produce long stringy chips; cast iron and steel hog harder and chip more granularly. High-speed steel tools can hog across a wider range of speeds; carbide cutters need higher spindle rpm but can push even harder before wearing.
A roughing end mill or roughing insert with chip breakers and a negative rake is the standard tool. Feeds and speeds are set to keep the tool load high without exceeding machine power or tool strength. Multiple hogging passes on a large blank are common; the first pass might be 0.200 to 0.500 inches deep, the second pass clears the rest, leaving a small finishing stock of 0.010 to 0.050 inches. The goal is to minimize total time by maximizing material removal per minute, accepting that the bore or face will need a finishing pass.
Hogging fails when the tool becomes dull. A worn roughing insert generates heat, walks across the surface instead of cutting cleanly, and eventually breaks. Coolant helps, especially on harder materials: it reduces built-up edge, carries away chips, and extends tool life. In dry hogging, chips pack around the tool and workpiece; in flood-cooled setups, chips flush away.
The term comes from the verb 'to hog': to consume greedily and messily. In machining, the cutter is greedy for material. Hogging is the opposite of precision work; it is the heavy, fast, necessary first step on the way to a finished part.