"In buying them, you must always give two numbers—the length, in inches, and the diameter. This is the diameter of the wire forming the body and runs from 0 to 30, number 0 being about 1⁄16 inch.
"A one-inch screw No. 8 would be fatter or larger in diameter than a one-inch No. 6, which is of comparatively slight or thin proportions. They are sold in boxes containing a gross.
"In fastening two pieces of wood together, they should be prepared as shown at a ([Fig. 119]) for a flat head and as at b for a round head. The screw slips through the first board, and the screw threads engage only in the second in each case."
[XXI]
BORING TOOLS
"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].)