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Full text of "Modern Mechanical Engineering Vol-I"

104
PATTERN-MAKING
by a spring plunger taper pin working in holes in a quadrant and having an
index, by which the depth of cut may be predetermined and the cutter
gradually fed into the work.
The work-table is massive, and is provided with tapped holes to secure
holding-down clamps. It has two motions at right angles, one operated by
rack and pinion, the other by screw and hand-wheel. It is mounted on a
pillar that travels along a runway which is bolted to the main frame. The
base of the pillar runs on anti-friction rollers, and is moved by rack and pinion.
The table can be turned through a complete circle on the pillar and locked,


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Fig. 86.-Mechanical Wood-worker operating on Sectional Work of large Radius.   Any length
may be operated upon
and can be raised and lowered. An auxiliary table turning about a centre
pin is provided for small work.
The Range of Work Done.-Fig. 85 illustrates the cutting of the teeth
of a spur pinion, done in about nine minutes, a fair day's work if done by
hand. It is held in the universal head that is used for spiral and helical
gears. A gear-cutting fixture is inserted in the spindle, carrying a fly-
cutter having the same section as the tooth spaces.
Another large group of work is that which concerns the cutting of sweeps,
done at the bench with gouges, spokeshaves, and planes. They are cut with
an adze block (fig. 86), the spindle being set vertically, or canted slightly
if taper is required. The table carrying the sweep is moved around the curve,
round the centre of the top table if of moderate radius, or attached to a light
former of wood as in the figure for larger radii, the table being moved along