Fig. 122. The expansive bit
"The tool has certain limitations, of course. It is made in two sizes; one will bore holes of any size from 1⁄2 inch up to 11⁄2 inches, and the other any size from 7⁄8 inch to 3 inches, while extra lips or cutters are made to bore as large as 4 inches, but if you ever try to bore a hole of this size you will want all your muscle."
The screw-driver bit is simply a screw-driver with a bit shank instead of a wood handle, and the countersink has a cone-shaped end with enough grooves cut in it to give one or more cutting edges. Its use was illustrated in making the bench hook and shooting board.
Fig. 123. The Forstner bit
The gimlet bit may be used for boring holes for screws. It is made from 2⁄32 inch up to 12⁄32 inch, and is valuable for preparing articles for the smaller-sized screws where the auger bit would be too large.
We find for sale drill bits for electricians, warranted to go through a nail if necessary, and dozens of special bits.