Properly shaped drills' points are represented by Figs. 854, 855, 856, and others shown near them. To make a drill cut easily, and to allow sufficient room for the shavings detached to get out of the drill hole, it is requisite that the portion immediately adjoining the point be of less extreme diameter than the extreme diameter between the two cutting edges. This diameter is termed the drill's size ; and the difference between the size and the narrower part adjoining, is termed the clearance. When the clearance is not sufficient the shavings become wedged between the drill's end and the sides of the hole and breaks the drill. But when the clearance is too great the drill is rendered very unsteady while cutting, which causes the hole to be rough and also tends to break the drill. A drill with this defect is also more liable to bore a crooked hole, than a drill which has only a proper amount of clearance. In addition to this there is an advantage in a properly formed drill not being much reduced in size by the grinding for sharpening.

The greatest amount of a drill's clearance exists at the place where the taper part of the drill's end terminates and the parallel part begins. At this place the diameter of the parallel portion for general purposes, should be about eight-tenths, or seven-tenths of the drill's size, which will provide a medium amount of clearance for general work, whether the holes to be made are small or large.

Figs. 854 and 855 represent drill-points whose cutting edges subtend an angle of about seventy-five or eighty degrees, which is that required to prevent the drill-point getting out of position while drilling, and thereby making a rough hole or shaking the drill. Such a shape will suit brass, iron, or steel; but if more pointed the point would break with the pressure which is applied while cutting. The end shown by Fig. 855 is more suited to hard iron and steel, being thicker than that shown by Fig. 854.

Drill-ends having grooved points for obtaining keen edges without much strength, which were mentioned in page 260, are denoted by Figs. 859, 860, and 861. The one shown by Fig. 859 has a narrow groove; this is required to avoid using a comparative large portion of the end when it happens that its length is of importance. A wider groove which occupies a considerable length of the drill-point is seen in Fig. 860; this shape allows plenty of room for the shavings, and is that usually made with ordinary grindstones. By reason of such grooves being always adjoining the cutting edges, the drill-points are grooved to suit the character of the drill, whether left-handed or right-handed; a grooved point of a left-hand one being indicated by Fig. 861.

Right-hand drills are those denoted by Figs. 854, 855, 858, 859, and 860. Left-hand ones are those indicated by Figs. 856, 857, and 861. Of these two species those employed in any one machine are suited to the direction in which the machine's drill-spindle rotates ; some machines requiring right-hand drills, and others requiring left-hand ones. The drill-end represented by Fig. 858, is a right-hand one; and a view of the point is given for those who may wish to easily distinguish a right-hand point from one which is left-handed.