e same principle as auger-bits,
except that the spurs have no screw, and hence have to be pushed
forcibly into the wood. Sizes are given in 16ths of an inch. They are
useful for soft wood, and in boring large holes in thin material which
is likely to split. They are sharpened in the same way as auger-bits.

_Foerstner bits_, Fig. 133, are peculiar in having no spur, but
are centered by a sharp edge around the circumference. The size is
indicated on the tang, in 16ths of an inch. They are useful in boring
into end grain, and in boring part way into wood so thin that a spur
would pierce thru. They can be sharpened only with special appliances.

_Expansive-bits_, Fig. 134, are so made as to bore holes of different
sizes by adjusting the movable nib and cutter. There are two sizes,
the small one with two cutters, boring from 1/2" to 1-1/2" and the
large one with three cutters boring from 7/8" to 4". They are very
useful on particular occasions, but have to be used with care.

_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.

[Illustration: 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 sp