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The basic elements of a production drawing, including title block, dimensions, projection lines, leader lines, and dimensioning rules. It covers various aspects such as placement, orientation, and interruption of dimension lines, use of arrowheads and dots, and dimensioning in narrow spaces. The document also discusses the execution of dimensions and the use of shape identification symbols.
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Producing Drawing
component
or
part
drawing
is
termed
as
a^
production
drawing, if it facilities its manufacture. It is an authorizeddocument to produce the component in the shop floor.It
furnishes
all
dimensions,
limits
and
special
finishing
processes such as heat treatment, grinding, etc., in additionto the material used. It should also mention the number ofparts that are required for making of the assembled unit, ofwhich the part is a member.
Production drawing of a component should also indicatethe sub or main assembly where it will be assembled. It isnecessary
to
prepare
the
production
drawing
of
each
component on a separate sheet, since a craftsman willordinarily make one component at a time. However, insome cases, the drawings of related components mayalso appear on the same sheet. Figure 1.2 shows theproduction drawing of a jig bush.
Need for a production drawing The
graphic
representation
of
a^
product,
starts
at
the
transformation stage of ideas into a drawing by a designengineer.
production
drawing
is
a^
complete
working
drawing, representing all the details of the product, regardingsize, shape, material, process, tools and equipment.The
craftsman
is
completely
guided
by
the
production
drawing, during the manufacture of the product. Hence, anymistake in a production drawing will result in loss of time,money
and
decreased
productivity.
Further,
it^
is
a^
legal
document while going for subcontracting of works. Hence, aproduction drawing should be prepared without any scope formore than one interpretation.
The design engineer uses orthographic or pictorialviews
to
record
his
ideas,
free
hand.
These
are
called working sketches. These sketches are usedfor both the component and assembly drawings.The working drawings are sent to the shop, in theform of blue prints, ammonia prints or other similarforms of reproduction. Therefore, the drawings mustbe made as tracings.
components, and
Drawing Sheet Sizes Drawing paper and cloth are available in rolls of variouswidths
and
in
standard
trimmed
sizes.
Most
of
the
draughting
rooms
use
standard
sheets,
printed
with
border and title block. There are five standard sizes fordrawing
sheets
(First
choice),
specified
by
Bureau
of
Indian Standards (BIS) SP: 46-1988, as given below. Thestandard sizes help save paper and are also convenientfor storing.
Drawing sheet layout The layout of a drawing sheet should, by the clarity andneatness
of
its
appearance,
facilities
the
reading
of
the
drawing. It should also facilitate essential references to belocated easily.Borders, enclosed by the edges of the trimmed sheet and theframe, limiting the drawing space shall be provided with allthe sheet sizes. It is recommended that these borders have aminimum width of 20 mm for the sizes A0 and A1 and aminimum width of 10 mm for other sizes. A file margin fortaking perforations may be provided on the edges, far left ofthe title block. It should have a minimum width of 20 mm.
Four centering marks shall be provided in order to facilitatepositioning of the drawing, when reproduced or microfilmed.Two
orientation
marks
may
be
provided
to
indicate
the
orientation of the drawing sheet on the drawing board.It is recommended to provide on all drawings, a figurelessmetric reference graduation, with minimum length of 100mm and divided into 10 equal parts. The metric referencegraduation shall preferably be disposed symmetrically aboutthe centring mark, near the frame in the border, with aminimum width of 5 mm.
The pre-printed drawing sheets when used, should include
the following features:
i)^
metric
reference
graduation,
ii)
grid
reference
system, and iii) trimming marks.
Fig. 2 represents a typical layout of a drawing sheet.
Fig. 2
production
drawing
may
include
the
following
additional
information,
located
either
in
the
drawing
sheet or in the title block:
general
note
on
tolerance
on
dimensions,
not
individually toleranced,
Information on a drawing Every drawing should be numbered. Some companies useserial numbers such as 70524 or a number with prefix orsuffix,
or
Many
different
numbering
systems are in use, in which various digits of the drawingnumbers indicate different things, such as model number ofthe machine and the general nature or use of the part.If all the drawings are made to the same scale, the scaleshould be indicated in or near the title block. Otherwise, theindividual scales should be indicated below the respectivedrawings.
General notes can be given on the working drawings tospecify the tolerances of dimensions.According to the BIS SP:46-1988, Engineering drawingpractice for schools and colleges; first angle projectionmethod only, is required to be followed.Specifications
regarding
general
notes,
material,
heat
treatment, finish, general tolerances and number requiredare located on or near the title block.
