Besides the ordinary tools in use, as gimlets, bradawls, pin and brace
bits, augers, &c., which do not need description, the following are
noteworthy:--
=521.= Is the =ordinary ~V~ drill= for metal work.
=522. Flat point,= or “bottoming” drill.
=523 & 524. Countersinking drills= for metal.
=525. Centre bit= for wood.
=526. Twist bit= for wood; clears its own borings. There is a variety
with rounded cutter edges.
=527, 528, & 529. Rock drills,= or “jumpers.”
=530. Earth borer,= or mooring screw.
[Illustration: 512.-530.]
=531. Twist drill= for metal.
=532 & 533. Countersinking drills= for wood.
=534. Diamond drill= for rock; bores an annular hole, the core of which
breaks out at intervals.
=535 to 545. Well boring tools= for different kinds of strata; tools for
raising broken rods, &c.
=546. Hollow boring cutter= for cutting a shoulder on a central core;
dowelling bit.