The particular class of drifts represented by Fig. 333 and others adjoining, are cutting drifts, and consists of angular tools having cutting teeth extending from the sides or faces ; such tools are employed for enlarging holes, such as key-ways, and joint-pin holes, this being effected by driving the drift through the work with hammering. Cutting drifts for making parallel holes are thickest at a short distance from the extremity which is first put into the work, and by hammering a drift until its thickest part has cut its way entirely through the length of a hole, the hole is made parallel without a tedious filing. When it is requisite to enlarge a hole by cutting on all its four sides, a drift is used having teeth on all the four faces, resembling Fig. 333 or 334; but if it is necessary to enlarge a hole at only one side, or end, a drift having teeth on only one side is employed for the purpose; a tool of this kind is indicated by Fig. 335. Cutter drifts that are taper, similar to Fig. 336, are useful for making taper square holes. One important use for cutter drifts, whether for parallel holes or taper ones, is that of making a large number of holes to one shape and thickness, this being effected for parallel holes by merely driving the drift through the hole or holes which were previously roughly formed by drilling and chiselling. To make a number of taper holes to one size, the drift is hammered to a certain distance which is indicated by a mark on the drift.