"Boring tools are very interesting," said Ralph. The brace and bit
for soft woods have practically taken the place of the old fashioned
augers, gimlets, etc. The reason is not hard to find. An auger or
gimlet could bore but one size of hole, while with a brace and set of
bits almost any diameter can be secured. A little later on, I'll tell
you about a Yankee invention along this line.
"The brace is a sort of universal tool holder, and any tool designed to
fit into it is known as a bit, as for example a countersink bit, or a
screw driver bit, and several varieties of drills.
"The shank, or part that fits into the brace, is usually square and
tapering, and the part of the brace which engages this shank is called
the 'chuck.' (Fig. 120.)
"The centre bit, an old-fashioned form, had all the necessary features
of a good boring tool but one. It had a sharp centre for accurately
locating the hole, a knife edge for cutting the fibres, and a chisel
for removing the wood, but it lacked the spiral screw thread of the
modern tool, and had to be forced through the wood by main strength. On
a modern auger bit, this spiral screw relieves the worker of a large
part of the labour; all he has to do is to turn the brace and keep it
straight, supposing of course that the bit is sharp. (Fig. 121.)
[Illustration: Fig. 120. Gimlet bit and centre bit]
"The auger bit is most commonly used by woodworkers. It has two knife
edges and two chisels besides the spiral spur in the centre. A short
form of this tool, called the dowel bit, has the advantage of bending
less readily than the ordinary auger bit. The size in sixteenths of
an inch is stamped into the metal shank, but if this number is not
distinct or for any reason is missing, the diameter may be measured by
holding the rule across the knife edges."
[Illustration: Fig. 121. The auger bit]
"What's the Yankee invention you were going to tell me about?"
interrupted Harry.
"Well, suppose you wanted to bore a large hole, say 2-1/2 inches in
diameter, the probabilities are that you wouldn't have a bit that size.
In fact, to have a full set of bits from 3/16 inch up to 3 inches would
mean a very expensive lot of tools. This difficulty has been overcome
by a very clever invention called the extension or expansive bit. (Fig.
122). On this tool the knife edge and chisel are part of a moving lip,
which may be fastened at any desired point by means of a set screw.
"Besides being adjustable in diameter, the lip of the bit has a scale,
and the body a single line engraved on it. By bringing this line to the
various measurements on the scale, you can set it to a definite size
without the trouble of measuring it.
"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 1-1/2 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."
[Illustration: Fig. 122. The expansive bit]
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.
[Illustration: 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.
In working with thin wood, the auger bit is very apt to split it,
especially brittle woods, like red gum. Even this contingency is
provided for in the Forstner bit, which will bore a hole in a sheet of
paper (Fig. 123), and is therefore very valuable for work in veneering
or other very thin material.
The brace is represented by several styles and makers, but the beginner
must look for the same qualities in the brace as he would in any other
tool--good workmanship and material, simplicity and durability.
The old-fashioned Spofford brace was strong, simple, and reliable. For
working in corners or any place where a full revolution of the tool is
not possible, a ratchet attachment is necessary. This is found on most
of the modern tools, and may be obtained at any hardware store. (Fig.
124).
[Illustration: Fig. 124. Common types of the brace]
The hand drill (Fig. 125) is one of the most useful tools any one can
have about the shop or the house. To be able to make holes in soft
or hard wood, tin, zinc, brass, copper, or iron is certainly a great
advantage, and some form of the tool should be in every establishment.
Our boys found it useful in making moving toys, wind vanes,
anemometers, and dozens of other pieces, and never regretted its cost.
It may be bought for fifty cents and upward, a very good one costing
about $1.50. The drills designed to be used with this tool vary by 1/64
inch, beginning with 5/64 inch up to 3/8 inch. Above this a larger
chuck is required. They have round shanks instead of the ordinary
square bit shank.
[Illustration: Fig. 125. The hand drill]