Ground Machined Worm Bore Diameter 8 mm Bore Diameter Tolerance +/- 0.2 mm Bore Type Plain Face Width 30 mm Finish Black Oxide Gear Shape W1 Hub Diameter 20 mm Hub Projection 10 mm Material Carbon Steel Maximum Teeth Hardness 194 HB Metric Module Pitch 1.5 Number of Starts 2 Outside Diameter 28 mm Overall Length 40 mm Pitch Diameter 25 mm