A bench grinder is a portable version of larger, industrial grade grinding machines found in many machinist and metal working shops. a bench grinder is a portable version of larger, industrial grade grinding machines found in many machinist and metal working shops. they spin at high speeds to remove material, which can be anything from wood to metal, by abrasion.. Woodcraft 150780 (8") wheels: 60- and 120-grit aluminum oxide rpm: 1,790. editor test-drive: this affordable, single-speed grinder doesn't offer a task light or a dressing tool, but in exchange you get high-quality, aluminum-oxide wheels meant for sharpening tools. and for what those wheels would cost as an upgrade, you could easily add a light and dressing tool, and still be money ahead..