Patent Pending Spline Tool.
The two ends of the cable are fixed, after a few windings in the opposite direction, on each side of the groove of the pulley. The pulley is attached to the head of the lathe by a clamping collar.
Access to the collar screw is through a hole in the groove of the pulley.
For added safety, tension can be released on the lathe drive belts.
Pulleys of different diameters make it possible to vary the pitch of the spiral of the spline.
The two references which align the cable on each side of the pulley are mounted, with the tube, on a base which can be moved back and forth to adapt to parts of different diameters or of conical shape.
The tension pulley puts tension on the cable. The tube stabilizes the movement of the carriage. Both are mounted on a small plinth that can be moved back and forth to accommodate workpieces of different diameters.
To groove a non-linear part, the tube is removed and the carriage is guided by a small stud located at the base of the carriage which slides against a jig fixed to the table, a jig which exactly matches the curve of the part to be cut.
A possible improvement to the system would be to mount the router to the carriage by a small mobile part which would allow the bit to be released when re-indexing the part to be splined without the spline going all the way to the end of the part. Currently if you want to stop the cut before the end of the part there must be a small collar at the end of the groove which serves as a clearance when the part is reindexed. (By 2021 a hinged router base was added.)
A small clamping block mounted on the carriage makes it possible to secure it to one or the other cable and thus, by its movement, to cause the rotation of the part in one direction or the other.
Adjusting the router bit adjusts the depth of cut.