I want to design and create a gearbox that allows an input shaft to be continuously rotating in one direction, while the output shaft rotates one full turn in the same direction but then half a turn in the opposite direction and repeat that cycle.
The application for it would be attaching to a drill and automatically tap holes to cut threads.
The only way I can see it working at the moment is by creating a gear which has teeth missing so that it rotates to a certain point (1 full turn of output) and then slips, being pulled back by a return spring) and hits a stop to restrict back rotation to half a turn.
However I have concerns about the reliability of this design and the fact that it would be difficult to allow it to work in both directions.
Having a mechanism that can operate in both directions by changing the rotational direction of the input shaft is ideal because it would allow it to be used to cut both right and left hand threads.
Any ideas about how to achieve such a gearbox would be greatly appreciated.
And sorry if this sounds really confusing, it’s quite difficult for me to explain.