201
UNIT 11
Machining Specifications
and Drawing Notes
A
I 3
4
5
B
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F
G
2
After completing this unit, you will be able to:
Identify and interpret general notes on a print.
Identify and interpret local notes on a print.
Read and interpret specifications for holes and
additional processes such as counterbores and
countersinks.
Read and interpret callouts for common machining
processes such as necks, keyways, and knurls.
Additional information must often appear on
a drawing to provide information and instructions
beyond the title block information, list of materials,
graphic shape description, and basic dimensioning.
These additional annotations are usually classified
as notes, specifications, or callouts. Notes can be
used to eliminate repetitive information or to give
more information about the size of holes, fastener
types, or other special specifications for removal of
machining burrs.
Sometimes notes can contain so much
information that placing the note on the drawing
makes the drawing unreadable. This is often the case
for architectural and structural drawing specifications.
For these notes, the information is typed or printed
on separate sheets. The sheets are then included
with the set of drawings. This is from where the term
“drawings and specifications” is derived.
Many large industries have internal process-
specification manuals. These manuals may specify
how to annotate a drawing so the machinist
has information on how to perform machining
processes—the machine, tools, and cutters to be
used, as well as the tolerances. Most current drafting
standards discourage the practice of putting all of
these processes on the drawing, allowing any vendor
or supplier to choose their own processes, as long
as the part matches size and location dimensions.
As is common, older drawings will use different
standards and must be read by the print reader. You
should become familiar with the standards used by
your company and the processes involved in the
work you are required to perform. This unit will
help provide you the knowledge needed for this.
Notes
Basically, notes are classified as either general
or local, but both types of notes can contain similar
information. The type of note is determined by the
application of the note and how it is placed on the
drawing. General notes apply to the entire drawing.
They are usually placed in a horizontal position
above or to the left of the title block. General notes
are not referenced in the list of materials or from
specific areas of the drawing. Some examples of
general notes are given in Figure 11-1.
Sometimes there are exceptions to general
notes indicated in local notes. In this case, the
general note is followed by the phrase
EXCEPT AS
SHOWN
or
UNLESS OTHERWISE
SPECIFIED. The
general note then applies to the entire part or to the
entire drawing, except where a difference is noted
by a local note.
Figure 11-1.
General notes apply to the entire drawing.