Drills and drilling

For drilling holes both the joiner's ratchet-bit or arm-brace with ball-bearing head (68:1) and the hand-drill (68:2) are used. The ratchet-brace is designed for slow, powerful cutting, usually with wing-bits having a square taper shank. The alligator jaws will also accept standard twistdrills with parallel shanks up to 3/8 in (9.5 mm) diameter, although they are inclined to slip under load if the jaws are at all worn.

This brace can be obtained in a range of sweeps, i.e. the circle through which the arm turns, from 8 in (203 mm) to 14 in (355 mm), with the larger sweeps yielding the greater power; while for confined spaces the electrician's ratchet-brace with 5 in (127 mm) sweep is invaluable. The standard hand-drill (68:2) is designed for the rapid boring of small-diameter holes, and has a three-jaw chuck accepting 1/4 in (6 mm) or 5/16 in (8 mm) parallel shank bits and drills. For larger shank sizes up to 1/2 in (12.5 mm) diameter the engineer's pattern two-speed drill with breast-pad for extra power is necessary. These hand-drills will not accept taper shank bits.

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