WHEN A WORM IS NEEDED TO MESH WITH A SPUR GEAR WITH SHAFTS AT RIGHT ANGLES, IT MAY BE FIRST ROUGHED OUT BY ORDINARY THREADING METHODS AND THEN FINISHED TO CORRECT FORM IN A LATHE WITH A STRAIGHT-SIDED TURING TOOL SET TO PROPER ANGLE AND AT THE PROPER DISTANCE OFF THE CENTER THE ANGLE OF THE CUTTING EDGE OF THIS TOOL, MEASURED FROM A PLANE PERPENDICULAR TO THE AXIS OF THE WORM, IS THE LEAD ANGLE OF THE WORM ON ITS BASE CYLINDER. THE DISTANCE OFF CENTER AT WHICH IT IS TO BE SET IS EQUAL TO THE RADIUS OF THE BASE CYLINDER. THE DATA FOR FINISH CHASING SUCH A WORM ARE DETERMINED AS FOLLOWS:

WHEN,

• ? = PRESSURE ANGLE OF SPUR GEAR AT R ₂

• N ₂ = NUMBER OF TEETH IN SPUR GEAR

• R ₁ = PITCH RADIUS OF WORM, INCHES

• R ₂ = PITCH RADIUS OF SPUR GEAR, INCHES

• C = CENTER DISTANCE, INCHES

• R _b1 = BASE RADIUS OF WORM, INCHES

• L = LEAD OF WORM, INCHES

• R _r1 = ROOT RADIUS OF WORM, INCHES

• P = CIRCULAR PITCH OF SPUR GEAR AT R ₂, INCHES

• C = CLEARANCE, INCHES

• R _o1 = OUTSIDE RADIUS OF WORM, INCHES

• R _o2 = OUTSIDE RADIUS OF SPUR GEAR, INCHES

• R _r2 = ROOT RADIUS OF SPUR GEAR, INCHES

• R _b2 = BASE RADIUS OF SPUR GEAR, INCHES

• ? _b = LEAD...