PRIN. OF DRAFTING AND SHOP DRAWINGS - OD1641 - LESSON 1/TASK 5
It is sometimes difficult to realize that the picture portion of a drawing is only
one part of the total finished drawing.
The title block, revision block, and
drawing notes are just as important as the picture portion, and often they are just
as time-consuming to prepare.
a. Assembly Drawings. Assembly drawings show several objects joined together. An
assembly drawing must include all information needed by the craftsman to correctly
assemble the parts. They do not usually include specific object dimensions which
are necessary for assembly.
Figure 88 (on the following page) illustrates an assembly drawing. Each object is
identified by part number, but it is not dimensioned.
Hidden lines have been
omitted to make the drawing easier to read.
This is not always possible,
especially for assemblies that contain internal parts.
If any specific operation is to be performed by the assembler, it must be noted on
the assembly drawing. For example, if several parts are to be joined together by a
bolt, the bolt hole should, if possible, be drilled during the parts assembly to
ensure that all the parts align properly.
Assembly drawings sometimes reassign new part numbers to the various component
pieces that make up the assembly.
Assembly numbers are usually one or two digit
numbers (1, 2, 3, 14, 22, etc.) and are added to save printing the larger, more
complicated part numbers on the assembly drawing.
If assembly numbers are used,
include them in a column in the parts list next to and to the left of the part
b. Detail Drawings.
They are a set of instructions that should include all
information necessary for the complete and accurate manufacture of the object.
They should include, among other things, a complete size and shape definition of
the object; the material from which the object is to be made; all necessary
information on the treatment of the materials; surface finish requirements;
references to applicable specifications; any necessary inspection information; and,
if necessary, instructions for handling the finished object.
Figure 89 (on page
102) illustrates a detail drawing.