Most delicate measurements must be made, however, to discover that not only the width but the thickness increases from A to B, and decreases from C to D. How carefully this tapering must be done can be realized when we know that the difference in thickness from A to B is only three one-thousandths of an inch, and from C to D twelve one-thousandths at end A and five one-thousandths at end B.
Fig. 15. Method of holding the Saw
The saw should be held in the right hand, with the left grasping the board. The thumb of the left hand acts as guide, the saw is tilted, as shown in [Fig. 15], and drawn toward the worker at the first stroke. This tool should be used without exerting much pressure, in accordance with the general rule that we do our best work with tools when we work easily and deliberately.
Fig. 16. The Backsaw
Many varieties of saws are designed for special purposes, including those which cut stone and metal.
Fig. 17. Method of using the Backsaw and Bench Hook
6. Backsaw. The backsaw is a crosscut saw with small teeth, and has a heavy steel backpiece, [Fig. 17], to prevent bending. In this respect it differs from the ordinary crosscut varieties, which bend readily. The purpose of the backsaw is to make fine, straight cuts in delicate, accurate work. The steel back B is necessary on account of the thin blade, but on account of the thickness of B no cut can be made deeper than the line C. This tool will cut in any direction with reference to the grain, but is primarily a crosscut saw.