In boring work chucked and revolved in the lathe, such, for instance, as axle-boxes for locomotives, the boring-bar here shown is an excellent tool. A represents a cutter-head, which slides along, at a close working fit, upon the bar, D D, and is provided with the cutters, B B B, which arc fastened into slots provided in the head, A, by the keys shown. The bar, 1) I), has a thread cut. upon part of its length, the remainder being plain, to fit the sliding head. One end is squared to receive a wrench, which, resting against the bed of the lathe, prevents the bar from revolving upon the lathe centre, F F, by which the bar is held in the lathe. G G G are plain washers, provided to make up the distance between the thread and plain part of the bar, in cases where the sliding bead, A, requires considerable lateral movement, there being more or fewer washers employed according to the distance along which the sliding head is required to move. The edges of these washers are chamfered off to prevent them from burring easily. To feed the cutters, the nut, II, is screwed up with a wrench.

Boring Bar

Boring-Bar

The cutter head, A, is provided in its bore with two feathers, which slide in grooves provided in the bar, D D, thus preventing the lead from revolving upon the bar. It is obvious that this bar will, in consequence of its rigidity, take out a much heavier cut than would be possible with any boring-tool, and furthermore that, there being four cutters, they can be fed up four times as fast as would be possible with a single tool or cutter.