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Full text of "Modern Mechanical Engineering Vol-I"

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with shoulders and held similarly. Roughing-cutters in fig. 29 are each
adjusted with a grub-screw and locked with a nut. Cutters are set spirally,
and tightened with tapered pins in splits. Wedge bushings and screws are

FJg. 29.—" Wrigley " High-speed Cutters for Aluminium, adjusted with Screw and locked with Nut

used for tightening,
feet in diameter.

Many of the heads with inserted cutters are several


Grinding Wheels.—The old term " emery " wheels applied to this
group has long been abandoned, since emery is employed to a limited
and ever-lessening extent, having been replaced by more effective grinding

Emery and Corundum.—The difference between these is one of
purity. Alumina is the chief constituent of each. Corundum contains a
higher proportion of alumina than emery, and its grains split, leaving sharp
edges; while emery wears smoothly, with a glazed surface. Both materials
are impregnated with oxide of iron, which, when present in large quantities,
reduces the cutting capacity. On the other hand, emery wheels produce a
high finish.

Carbide  of  Silicon Abrasives.—These are prepared in electric