[Footnote 1: A Paper by Chas. T Porter, read before the American
Society of Mechanical Engineers.]
The system of keeping drawings now in use at the works of the
Southwark Foundry and Machine Company, in Philadelphia, has been found
so satisfactory in its operation that it seems worthy of being
communicated to the profession.
The method in common use, and which may be called the natural method,
is to devote a separate drawer to the drawings of each machine, or of
each group or class of machines. The fundamental idea of this system,
and its only one, is, keeping together all drawings relating to the
same subject matter.
Every draughtsman is acquainted with its practical working. It is
necessary to make the drawing of a machine, and of its separate parts,
on sheets of different sizes. The drawer in which all these are kept
must be large enough to accommodate the largest sheets. The smaller
ones cannot be located in the drawer, and as these find their way to
one side or to the back, and several of the smallest lie side by side
in one course, any arrangement of the sheets in the drawer is out of
the question.
The operation of finding a drawing consists in turning the contents of
the drawer all up until it is discovered. In this way the smaller
sheets get out of sight or doubled up, and the larger ones are torn.
No amount of care can prevent confusion.
Various plans have been adopted in different establishments intended
to remedy this state of things, but it is believed that none has been
hit upon so convenient, in all respects, as the one now to be
presented.
The idea of keeping together drawings relating to the same machine,
or of classifying them according to subjects in any way, is entirely
abandoned, and in place of these is substituted the plan of keeping
together all drawings that are made on sheets of the same size,
without regard to the subject of them.
Nine sizes of sheets were settled upon, as sufficient to meet our
requirements, and on a sheet that will trim to one of these sizes
every drawing must be made. They are distinguished by the first nine
letters of the alphabet. Size A is the antiquarian sheet trimmed, and
the smaller sizes will cut from this sheet, without waste, as follows:
A, 51×30 in.; B, 37×30 in; C, 25×30 in.; D, 17×30 in.; E 12½×30
in.; F, 8½×30 in.; G, 17×15 in.; H, 8½×15 in.; I, 14×25 in.
The drawers for the different sizes are made one inch longer and wider
than the sheets they are to contain, and are lettered as above. Those
of the same size, after the first one, are distinguished by a numeral
prefixed to the letter. The back part of each drawer is covered for a
width of from six to ten inches, to prevent drawings, and especially
tracings, from slipping over at the back.
The introduction of the blue printing process has quite revolutionized
the drawing office, so far at least as we are concerned. Our drawings
are studies, left in pencil. When we can find nothing more to alter,
tracings are made on cloth. These become our originals, and are kept
in a fire-proof vault. This system is found admirably adapted to the
plan of making a separate drawing for each piece. The whole combined
drawing is not generally traced, but the separate pieces are picked
out from it. All our working copies are blue prints.
Each drawer contains fifty tracings. They are two and a half inches
deep, which is enough to hold several times as many, but this number
is quite all that it is convenient to keep together. We would
recommend for these shallower drawers.
Each drawing is marked in stencil in the lower right hand corner, and
also with inverted plates in the upper left hand corner, with the
letter and number of the drawer, and its own number in the drawer, as,
for example, 3F--31; so that whichever way the sheet is put in the
drawer, this appears at the front right hand corner. The drawings in
each drawer are numbered separately, fifty being thus the highest
number used.
For reference we depend on our indices. Each tracing, when completed,
is entered under its letter in the numerical index, and is given the
next consecutive number, and laid in its place.
From this index the title and the number are copied into other
indices, under as many different headings as possible.
Thus all the drawings of any engine, or tool, or machine whatever,
become assembled by their titles under the heading of such particular
engine, or tool, or machine. So also the drawings of any particular
part, of all sizes and styles, become assembled by their titles under
the name of such piece. However numerous the drawings, and however
great the variety of their subjects, the location of any one is, by
this means, found as readily as a word in a dictionary. The stencil
marks copy, of course, on the blue prints, and these when not in use
are kept in the same manner as the tracings, except that only
twenty-five are placed in one drawer.
We employ printed classified lists of the separate pieces constituting
every steam engine, the manufacture of which is the sole business of
these works, and on these, against the name of every piece, is given
the drawer and number of the drawing on which it is represented. The
office copies of these lists afford an additional mode of reference
and a very convenient one, used in practice almost exclusively. The
foreman sends for the prints by the stencil marks, and these are thus
got directly without reference to any index. They are charged in the
same way, and reference to the numerical index gives the title of any
missing print.
We find the different sizes to be used quite unequal. The method of
making a separate tracing of each piece, which we carry to a great
extent, causes the smaller sizes to multiply quite rapidly. We are
marking our patterns with the stencil of the drawing of the same
piece; and also, gauges, templets, and jigs.
It is found best to permit the sheets to be put away by one person
only, who also writes up the indices, which are kept in the fire
proof.
We were ourselves surprised at the saving of room which this system
has effected. Probably less than one-fourth the space is occupied that
the same drawings would require if classified according to subjects.
The system is completely elastic. Work of the most diverse character
might be undertaken every day, and the drawings of each article,
whether few or many, would find places ready to receive them.
* * * * *