Fig. 1069.
Fig. 1070.
For larger work a table, such as shown in [Fig. 1068], is used, the cavity c permitting the drilling tool to pass through the work, there being a hole h provided for that purpose. The stem s fits in place of the dead centre. For cylindrical work the rest or chuck shown in [Figs. 1069] and [1070] may be employed. It consists of a piece fitted to the tail spindle in place of the dead centre, its end being provided with V-grooves. These grooves are made true with the line of centres of the lathe, so that when the work is laid in them it will be held true. It is obvious that one groove would be sufficient, but two are more convenient—one for large work and one for small work—so that the side of the shaft to be drilled shall not pass within the fork, but will protrude, so that the progress of the work can be clearly seen. In [Fig. 1070] an end view of this chuck is shown. It may be observed, however, that when starting the drill care must be taken to have it start true, or the drill may bend, and thus throw the work out of the true. For this reason the drills should be as short as possible when their diameters are small.
For square work this class of work table or chuck may be formed so as to envelop the work and prevent its revolving, thus relieving the fingers of that duty, and it may be so formed as to carry the work back or off the drill when the latter is retired after the drilling is performed.
Fig. 1071.
Another and quite convenient method of holding work to be drilled by a revolving drill in the lathe is shown in [Fig. 1071]. It consists of simply a bracket, a b, fitted to the tool-box of the slide rest, carrying a spindle with one end screwed to receive any face plates or chucks that fit the lathe live spindle. The bracket is kept in position by two pins in the under side of it, fitting into holes in the bottom piece of tool-box. If it be required to drill a straight row of holes, the spindle is fixed by the set-screws in its bracket, and the work is bolted to the face plate at the proper level, and traversed across opposite the drill in the lathe mandrel, by the cross screw of the slide rest, while it is fed up to the drill by the upper screw or the rack and pinion.