A holder is a tool for gripping a rod, axle, or other piece of work while it is being turned, the holder being fastened at one end of the work, and constituting the means whereby the rotatory motion of the lathe-spindle is imparted to the piece to be cut or otherwise modified. Holders are also named carriers, and are represented by Figs. 413, 414, 415. A general form of such tools is indicated by Fig. 413, which has a hole in the mid portion to receive work of various thicknesses, and one fixing screw, which is of sufficient length to allow the point to be screwed in to fix pieces of work whose thicknesses may be only about half the diameter of the hole in the holder. The holder shown by Fig. 414 consists of four pieces; of these, two are the grips that bite the work, and the other two portions are the fixing screws. Each of the grips has an angular gap, and these two gaps are important features of the instrument; being thus provided, the holder is capable of gripping a large number of pieces that are of different thicknesses, the two fixing screws being made of any desired length to make the holder suitable for its particular work. Fig. 415 denotes a strong class of holders having two levers by which the instrument is rotated; in the Figure these levers are shown by L. Through the tool being thus provided, its use is greatly extended, and may be used for other purposes in addition to the purposes of ordinary holders. The gripping power of the two holders shown by Figs. 414 and 415 is greatly superior to that of Fig. 413; but all such grips that are fixed by means of two screws require care while tightening the fixing bolts; during such fixing, while the work is between, both grips should be parallel to each other, if not, a severe tightening will not tend to secure the work, but to injure and in a short time to break the bolts.

Tommies

A tommy is a short lever having conical ends to enter holes in heads of bolts for screwing and unscrewing. The one shown by Fig. 416 is a simply formed tool having a loop at one end, which is a handle and a means for hanging the tool in its place. An arched tommy which is used for small lathes is denoted by Fig. 417 ; a tool of this shape can be used in many places and positions in which a straight tommy is useless. Tommies are indispensable for a large number of operations, such as fixing slide-rest screws, screw making with dies, drilling holes with crank-braces and ratchet-braces, and fixing carriers.