Patent ID: 8602841

Claim:
A grinding apparatus for forming threads on a chamfer portion and a finishing portion of a tap, the grinding wheel comprising: a. a body portion rotatable about a rotation axis and having a peripheral surface; b. a first rib extending around the periphery of the body portion and projecting radially outwardly from the peripheral surface between a first base portion and a first peak spaced radially outwardly from the first base portion, the first rib having a first leading side surface and a first trailing side surface, the first leading side surface and the first trailing side surface being inclined and extending between the first base portion and the first peak and converging toward the first peak, the first peak being radially spaced apart from the wheel axis by a first peak distance and the first base portion having a first width measured in the axial direction; c. a second rib axially offset from the first rib, extending around the periphery of the body portion and projecting radially outwardly from the peripheral surface between a second base portion and a second peak spaced radially outwardly from the second base portion, the second rib having a second leading side surface and a second trailing side surface, the second leading side surface and the second trailing side surface being inclined and extending between the second base portion and the second peak and converging toward the second peak, the second leading side being parallel to the first leading side surface and the second trailing surface being parallel to the first trailing side surface, the second peak being radially spaced apart from the wheel axis by a second peak distance that is less than the first peak distance, and the second base portion having a second width measured in the axial direction that is less than the first width; and d. a crest forming surface extending between the first side surface of the first rib and the second side surface of the second rib, the crest forming surface offset radially inwardly from the first crest by a radial distance that is substantially equal to a thread height of threads on a finishing portion of the tap and being configured to shape crests of threads on both a chamfer portion and the finishing portion of the tap.