[Fig. 1732], however, represents an excellent three-jawed chuck for driving drills, the bite being very narrow and holding the drill with great firmness.
Fig. 1733.
[Fig. 1733] represents a two-jawed drill chuck in which the screws operate a pair of dies for gripping parallel shank drills, the screws being operated independently.
In other forms of similar chucks the bite is a V recess parallel to the chuck axis, the only difference between a drill chuck for a drilling machine and one for a lathe being that for the former the jaws do not require outside bites nor to be reversible.
Holes that are to be made parallel, straight, cylindrically true in the drilling machine, are finished by the reamer as already described with reference to lathe work, and it is found as in lathe work that in order that a reamer may finish holes to the same diameter, it is necessary that it take the same depth of finishing cut in each case, an end that is best obtained by the use of three reamers, the first taking out the irregularities of the drilled hole, and the second preparing it for the light finishing cut to be taken by the third.
All the remarks made upon the reamer when considered with reference to lathe work apply equally to its use in the drilling machine.
