102 Modern Metalworking
it possible to accurately measure or lay out
angles. See Figure 6-17. The head also has a built-
in spirit level, allowing the tool to be used to set
up work requiring angular cutting.
6.3 MEASURING ANGLES
There are a number of angular measuring
tools employed in layout work in addition to the
protractor head of the combination set. These
tools are discussed next. The accuracy required
by the job will determine which tool must be
used.
Plain protractor. When angles do not have to
be checked or laid out to extreme accuracy, a
plain protractor will prove satisfactory. See
Figure 6-18. The head is graduated from 0° to
180° in both directions for easy use.
Protractor depth gage. This tool can be used
to check 30°, 45°, and 60° angles and measure
slot depths. See Figure 6-19.
Universal bevel. Auniversal bevel, Figure 6-20,
is useful for checking, laying out, and
transferring angles. Both the blade and stock
are slotted, making it possible to adjust the
blade into the desired position. A thumbscrew
locks it in place.
Vernier protractor. When a job requires
extreme angular accuracy, the machinist uses
a Vernier protractor. See Figure 6-21. This
tool enables the user to measure angles to
1/12 of a degree (5 minutes).
6.4 OTHER LAYOUT TOOLS AND
EQUIPMENT
Additional tools and equipment are
commonly used for a number of layout and
inspection tasks. These tools help produce an
accurate layout and meet the precision required
for the job.
Figure 6-16.
Locating the center of a section of round stock can be
accomplished by using a center head and rule.
Figure 6-17.
Angular measurements on layouts can be made with
the rule and protractor head of a combination set.
Figure 6-19.
Protractor depth gages are used to measure angles
and depths of holes. (L. S. Starrett Co.)
Figure 6-18.
A plain steel protractor can be used to measure or lay
out angles requiring only moderate precision.