First page: Screw cutting any lead on the lathe (from the standard gear box).
Explanations: look at the drawing here under.Using Thales theorema, the tool movement is the result of the B movement given by the carriage (standard lead) multiplied by the ratio AC/BC which can be adjusted by moving C.
Fully described in Moldel Engineer magazine issue 4270 (apr 2006).
Watch the video:
1 - The attachment is almost entirely contained in a toolholder (only a bench stop must be added).
2 - It works only for a short thread length from 50 to 90 mm Maxi according to the lead cut.
3 - The adjusting lever is graduated (and charts are given for the usual leads) for a quick and easy set up. But almost any lead can be machined within the
range of the gear box.
4 - No change gear is needed.
5 - The thread dial indicator can be used and the half nuts opened according to
the standard lead used.
This attachment is not a new idea: look at this "short thread cutting machine" contrived and made by the French horologist Antoine Thiout (1750)
This machine can be seen in Paris in this museum:
" Conservatoire national des ars et métiers"