[Hicks' Expanding Mandrel.]
Figs. 1, 2, 3.
Mention of this has been made in the body of the work. It is used for turning rings and washers, and various sizes of these can be turned upon the same mandrel, so that a set of three will suffice for all the work likely to be met with even in the largest factories. [Fig. 1] represents the mandrel complete. F, F is the central part, with a conical boss, A, cast upon it, and the whole turned with great accuracy. Four longitudinal dovetailed slots, seen plainly in [Fig. 3], are then planed in the conical part, and into these are fitted steel wedges, Fig. 2, A and B, and B, Fig. 3. C, Fig. 1, is a hollow conical washer, which can be advanced over the central part when driven forward by the nut D. This washer, acting on the ends of the sliding wedges, causes them to move towards the large end of the cone A, and, from the form of these and of the cone, any washer or ring will be held tightly when placed outside these wedges, and will also be mounted concentrically.
[Turning Spheres by means of Templates.]
It is but right to state that the above method has been objected to by a practical workman, whose business has led him to study the matter closely. He states that it is impossible in this way to effect the desired object. As the writer has not been able to test the working of the apparatus on his own lathe, he felt inclined, at first, to withdraw the whole chapter. The objections offered, however, were not, to his mind, entirely satisfactory; and the opinion of other equally scientific and practical men being favourable, the chapter has been retained. It is possible, nevertheless, that there may be a mathematical reason which the writer is not competent to work out, and the objector being a man of great mechanical knowledge and experience, his remarks are worthy of consideration. The practical (not insuperable) difficulty appears to be the production of a proper tool for this work.
[Plant's Geometric Chuck.]
This chuck is put in motion by an entirely new method; none of its parts being attached to the lathe head, the whole can be put in motion or released in an instant, and without stopping the lathe.
The whole of its work is executed by the continuous motion of the lathe, so that, when the chuck is adjusted, any figure (no matter how complex) may be begun and completed without once stopping the lathe.
By the different arrangements and adjustments of the chuck and slide rest, an infinite variety of the most beautiful geometrical figures may be produced; and some of them of so strange and fortuitous a nature as to bid defiance to any imitation.