Reamers, Fig. 135, are used for enlarging holes already made. They are made square, half-round and six cornered in shape.
Countersinks, Fig. 136, are reamers in the shape of a flat cone, and are used to make holes for the heads of screws. The rose countersink is the most satisfactory form.
Fig 138. Washer-Cutter.
The washer-cutter, Fig. 138, is useful not only for cutting out washers but also for cutting holes in thin wood. The size is adjustable.
3. CHOPPING TOOLS.
The primitive celt, which was hardly more than a wedge, has been differentiated into three modern hand tools, the chisel, see above, [p. 53], the ax, Fig. 139, and the adze, Fig. 141.
The ax has also been differentiated into the hatchet, with a short handle, for use with one hand, while the ax-handle is long, for use with two hands. Its shape is an adaption to its manner of use. It is oval in order to be strongest in the direction of the blow and also in order that the axman may feel and guide the direction of the blade. The curve at the end is to avoid the awkward raising of the left hand at the moment of striking the blow, and the knob keeps it from slipping thru the hand. In both ax and hatchet there is a two-beveled edge. This is for the sake of facility in cutting into the wood at any angle.
There are two principal forms, the common ax and the two bitted ax, the latter used chiefly in lumbering. There is also a wedge-shaped ax for splitting wood. As among all tools, there is among axes a great variety for special uses.