Measure effective diameter

Measure minor diameter

Measure major diameter

Measure pitch of the thread

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