A A. The foundation plate screwing on the plate of the mandrel and carrying the whole of the other parts of the chuck.

B, C. The two driving wheels giving an independent motion to the chuck.

D. Angular wheel moving freely on the wheel C for the angular adjustment of the figures.

E. Pinion of any number of teeth fitting on the shaft carrying D and C.

H. Large wheel of 120 teeth, forming the foundation of the second part, and driven from the pinion E by the wheels F, G, and T.