206 Print Reading for Industry
provide the inspector with an easier checking
distance, Figure 11-13. In similar fashion, sometimes
an undercut groove is used at the head of a
cylindrical part to eliminate the chance for a fillet
being created due to tool tip wear or a rounded
cutting tool. While local notes can be used to specify
the undercut, linear measurements that are easily
checked are preferred. See Figure 11-14.
Keyways
A key is a fastener used to prevent rotation of
gears, pulleys, and rocker arms on rotating shafts.
The key is a piece of metal that fits into a keyseat in
the shaft, which holds the key, or a keyway in the
hub, which allows the hub to slide over the key.
There are a variety of keys used in industry for
different situations. Examples of keys are shown in
Figure 11-15.
While a common practice at one time was to
indicate a keyway with a note, newer standards
promote the use of linear dimensions to specify exact
distances that are logical inspection distances. See
Figure 11-16. This technique eliminates confusion
regarding the size of the keyway. The older
method allowed the depth to be interpreted as the
height above the center of the curve, but it was also
sometimes interpreted to be the keyway sidewall.
Figure 11-12.
Chamfers on non-perpendicular surfaces should not be
dimensioned by note, but rather with dimensions.
Example 1 Example 2
Figure 11-13.
A ring groove or neck may be dimensioned by note
(example 1) or by dimensions (example 2).
Example 1 Example 2
Figure 11-14.
An undercut is sometimes used to help prevent corner
interference where a larger cylinder intersects a smaller
cylinder.
Gib-Head
Taper
Key
Square Key
Pratt
and
Whitney
Key
Woodruff
Key
Figure 11-15.
There are a variety of keys used in industry for different
situations.