A drill is a tool for making holes, or enlarging holes. Drills do not cut at any place along their sides, but at their ends. A drill for making holes where none exist, and which is easily made, and suitable for both iron and brass, is shown by Fig. 400. This drill is made of square steel, and the end, which is square and tapered, is suitable for a lathe, crank-brace, or ratchet-brace. The drill shown by Fig. 401 is made of round steel, and is fastened to its place by means of a small flat-bottomed gap in the conical portion. The square ends and conical ends of drills are their heads; these heads are the portions by which the drills are held in the drill-chucks. A drill-chuck is a drill-holder that is attached to the lathe when drilling is to be performed, and drills with cutting parts of various shapes and sizes have heads which are all alike, so that all may fit the holder.

Fig. 402 denotes a screw-drill. This tool is advantageous for drilling long holes, and is so formed that the diameter of the screw part is nearly equal to the diameter of the short straight portion at the end. A drill thus shaped is well guided by the screw without much friction, and the shavings are allowed free egress along the length of the thread-groove. The short straight end and the screw part adjoining are of a flat bar shape, the screw being made by twisting. Another screw-drill is denoted by Fig. 403, which has a longer screw and longer bearing; this drill is suitable for long holes, and may have either a square taper end, or a taper round end, for holding the drill in its holder. A good drill for making straight smooth holes is a cylindrical drill denoted by Fig. 404; this tool has a short flat portion at the cutting end, which is convenient to allow the tool to be several times ground without reducing the adjoining cylindrical part. Another good cylindrical drill is indicated by Fig. 405 ; this one has a few teeth for cutting, instead of a flat portion. The number of teeth in such a tool should be three, for drills not exceeding an inch in diameter, and for larger sizes the numbers of teeth may be five, seven, and nine. Both the screw-drills shown by Figs. 402 and 403 are adapted to make holes where none existed, but the cylindrical drills shown by Figs. 404 and 405 are only available for enlarging or finishing holes that were made with other drills. A half cylindrical drill is indicated by Fig. 406, and is very different in shape to the cylindrical ones, but the uses of both classes are the same, either tool being very efficient for making straight parallel holes, if the holes were commenced with another tool. In the Figures of the cylindrical drills, the letters G denote fluted grooves extending along the sides ; such grooves are not for cutting, but merely to admit oil and water, and to allow room for shavings.

When it is intended to make a hole so that its boundaries shall be straight, smooth, and parallel, and no hole exists at the place of the intended hole, the drilling commences with a simple pointed drill shown by Fig. 400, or 401 or 402 ; such a drill is first passed through the work to be drilled, and if only a small hole is to be made, the first drill may be large enough to leave only a sixteenth of an inch to be bored out for making the hole to the finished diameter; this sixteenth is next taken out with the finishing drill, which may be either a half cylindrical, or a cylindrical one. When a hole two or three inches in diameter is to be made by means of a small lathe, and no hole exists in the work, it is necessary to employ three or four drills previous to the finishing tool, in order that only a small amount shall be taken out during the final smoothing.