Abstract: A chip breaker includes an abutment surface having geometry generally corresponding in profile to the geometry on the cutting edge of the associated thread chaser to permit such abutment surface to be uniformly spaced from respective roots and crests of the thread chaser and in close proximity thereto when the chaser and breaker are clampingly juxtaposed. The juxtaposed or trailing surface of the chip breaker has angularly biased, parallel grooves therein to deliver coolant past the chaser body and then into the cutting area along the respective flanks of the chip breaker and chaser geometry.