Compound geometric chuck with change wheels

Compound geometric chuck with change wheels, in case

This is a chuck used in ornamental turning for producing cycloidal curves in great variety, It was invented by J. H. Ibbetson about 1815, and was a development of the geometric pen, an account of which was published by J. Baptist Suadi in 1752. The simple cycloidal chuck was known before 1815.

The geometric chuck consists of two parts, each of which produces an epicycloidal motion as the mandrel rotates. The interposition of one motion upon the other with the aid of change wheels enables a great number of designs to be constructed.

As the mandrel rotates, the first and second parts acquire a relative motion depending on the precise train of wheels chosen and may be made to trace any number of loops, each of which represents one revolution of the mandrel.

The work is mounted on the faceplate which rotates on an axis attached to the slide, and is driven by a train of wheels through a pinion which meshes with an internal and unseen train terminating in a wheel which is fixed to the slide of the first member, and which, therefore, revolves with the mandrel although eccentric to it. Thus the second part also generates a cycloidal motion and produces a number of loops which are interposed on the primary loops of the first part, which in turn are interposed on the circular motion of the back plate. By means of the slides the amplitudes of the motions may be varied, and a dividing wheel is fitted in each part to enable the curves to be placed in any particular position relative to one another or to the work.