Same as British chasing dial

One worm wheel and different dial

One worm wheel and one dial

More than one worm wheel and different dial

122

125

127

129

0.6403 x 1/10 Inch

0.6134 x 1/10 Inch

0.6304 x 1/10 Inch

0.6314 x 1/10 Inch

For easy thread cutting

To get proper, crest, flat, root radius and profile

To time saving

To reduce labour

Driver 30T, Driven 40

Driver 40T, Driven 50

Driver 50T, Driven 30

Driver 70T, Driven 50