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Full text of "Modern Mechanical Engineering Vol-I"


THE SHOPS                                  2"
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an intimate knowledge of the nature and scope of the operations performed
on hundreds of machine-tools is necessary. This devolves on the shop
manager, and on the foremen who have charge of the groups of machines,
as lathes, automatics, planers, gear-cutters, milling machines, grinders, and
so on. Each foreman must know the capacities and limitations of each of
the machines in the group of which he has charge, and must see that they
are operated to the fullest advantage. He will consult and discuss with the
shop manager respecting the best methods of machining certain articles. The
manager will decide the question of economies that may result by the trans-
ference of work from one group of machines to another, as from lathes to
turret lathes, from planers to milling machines, from lathes to grinders, and
so on. The foremen and manager jointly consider the question of the design
and employment of fixtures and jigs, and the relation of the expense which
they bear to the product. Detailed drawings are made in the office from
sketches supplied.
When the methods of machining have been determined, the details are put
on a definite basis by the foreman or the rate-fixer. Sketches are prepared,
or cards are written, stating precisely the nature and sequence of the several
machining operations involved, the tools to be used, the speeds and feeds, and
limits. Generally it is possible, as the work proceeds, to effect slight speeding-
up, which on a piece-work basis, or a bonus system, is to the advantage of
the machinist. But it does not lie with the attendant to make changes in the
general routine previously determined. That can only be done by suggestion,
with the consent of the foreman, or manager.
This organization includes all details. The grinding of tools of all kinds
is done in the tool-room, and they are checked out to the men, and returned
when they have become dulled with use. Gauges, jigs, and fixtures are treated
similarly, and they are corrected or renewed in the tool-room. In this
system nothing is tabulated by name. Every item, however insignificant,
has a number, or a letter, inserted on the drawings, and is checked out and
in by that.
The Tool-room.-This is a necessary growth, consequent on turret
practice, and on the employment of the multiple-edged cutters used on
milling machines, gear-cutters, and elsewhere. The set-up of boxes of tools
for turret work entails elaborate constructions and delicate adjustments.
The grinding of cutters can only be done on universal machines. Drills
are ground on machines. The standardized grinding of single-edged cutting
tools is done on machines. These functions are relegated to the men in the
tool-room, who also construct the smaller jigs and fixtures. Hence the
tool-room is a machine-shop in miniature, a microcosm complete in itself.
It contains a few machines of every class, in which universal designs are in
evidence, so that, having castings and forgings and bars supplied, the whole
of the work of tool-making in its widest sense is performed within its pre-
cincts, and tools are ground, repaired, set-up, and kept in working order,
ready for use in the shop.