AT TIMES THE OPERATION OF A MECHANISM MAKES IT NECESSARY TO HAVE A WORM DRIVING A SPUR GEAR WITH AXES AT RIGHT ANGLES, IN PARTICULAR WHEN AN AXIAL MOVEMENT OF THE SPUR GEAR IS REQUIRED WHILE IT IS REVOLVING. IN SUCH A CASE THE WORM MAY BE GENERATED ON A THREAD MILLING MACHINE WITH A STRAIGHT-SIDED THREAD MILLING CUTTER WHOSE AXIS IS SET PARALLEL TO THE AXIS OF THE WORM AT TIMES, IF THE LEAD ANGLE OF THE WORM IS APPRECIABLE, IT MAY BE NECESSARY TO CUT THE WORM DEEPER THAN THE STANDARD DEPTH TO PREVENT INTERFERENCE ON THE FILLET AT THE ROOT OF THE WORM THREAD. THE DATA FOR MILLING SUCH A WORM ARE DETERMINED AS FOLLOWS.

WHEN,

• ? = PRESSURE ANGLE OF SPUR GEAR AT R ₂

• N = 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

• R = RADIUS TO TOP OF FILLET ON WORM THREAD, INCHES

• R _oc = OUTSIDE RADIUS OF THREAD MILLING CUTTER, INCHES

• ? _C = HALF INCLUDED ANGLE OF THREAD MILLING CUTTER, AND ALSO LEAD ANGLE ON BASE CYLINDER OF WORM.

• L = LEAD OF WORM

• R _r1 = ROOT RADIUS OF WORM, INCHES

• R _r2 = ROOT RADIUS OF SPUR GEAR, INCHES

• P = CIRCULAR PITCH OF SPUR...