Its movements are such that the tools are guided by stops determining the length and the diameter of the work so as to make it exactly uniform, while the form of the cutting tools determines the form of the work, which must therefore be uniform.
The lathe may be described as one having a carriage rest spanning the bed of the lathe, which rest holds the work axially true with the lathe centres without the aid of the dead centre, while it at the same time trues the end of the work and leaves it free to be operated upon by other tools, which, after once being set and adjusted, shape any number of pieces of work to exact and uniform diameter and shape.
Fig. 719.
Fig. 720.
The manner in which this is accomplished is as follows: [Fig. 718] is a general external view of the lathe; [Fig. 719] is an end elevation view of the rest from the cone spindle end, and [Fig. 720] is an end view of the rest viewed from the tailstock end of the lathe. a is a ring fastened in the rest r by the set-screw b. The mouth c of the ring which first meets the work is coned, or beveled, as shown, and an opening on one side of the ring admits a cutting tool t. Now the work is placed one end in the cone driving chuck on the lathe spindle, and the other end in the cone or mouth c, [Fig. 719], being kept up to the driving chuck by the end pressure of c. As the work rotates, the tool t cuts it to the diameter d of the ring bore, the carriage or rest r traversing along the lathe bed as fast as tool cuts; hence the bore d serves as a guide to hold the work and make it run true, this bore being axially true with the lathe centres. The cone surface of c thus operates the same as the sole of an ordinary carpenter’s plane, the tool t cutting more or less rapidly according as its cutting edge is set to project more or less in advance of the surface of the cone or recess c. This admits of the tool cutting at a rate of feed that may best suit the diameter of the work and the nature of the wood. The tool t, is operated laterally to increase or diminish the rate of feed by the screw e, which also serves as a pivot, so that by operating the thumb-screw f, the tool point may be adjusted for distance from the centre of the bore d, or in other words the diameter to which the tool t will turn the work is adjusted by the thumb-screw f. g is the head of the pivot screw that the swing tool holder h works upon, and this swing motion carries the forming tool or cutter x, which shapes the work to the required form. i is a shaft upon which a lever, carrying the tool holder j, works, the latter carrying the severing tool k, which severs the finished work from the stick of wood from which the work is made.
The tool holders h and j are connected by means of the arms l and m to the stud o, fast in wheel p, operated by a knee lever q, which is pivoted at s to u, which is fast to one of the gibs that hold the carriage to the lathe Vs. The knee lever q is connected to the wheel p by a raw-hide strap, or belt v, so that the operator, by pressing his knee upon the end of the lever q, causes the wheel p, to partly rotate, carrying o with it (o being fast in p), and gives a forward radial motion to tool holder h and cutter x, causing the latter to enter the work until such time as the stud o and the screw stud w are in line, horizontally with the centre of the wheel p, after which tool holder h will move back, while the severing tool k (which has a continuous upward or vertical movement) is cutting off the finished work, which has been formed to shape, and reduced to the required diameter by the forward movement of the tool or cutter x. The object of the backward or retiring motion of h is to relieve the shaping tool x from contact with the work, while k cuts it off, or otherwise the work might meet x when cut off, and receive damage from contact with it. The stud w, connecting tool holder h with the wheel p, is threaded with a right and left-hand screw, by operating which the tool x may be operated to reduce the work to any required diameter.