PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 2
the gage are used for checking Unified and American threads, as well as
older American National or U.S. Standard threads, and for checking thread
cutting tools.
The center gage is also used to check the angle of lathe
centers. The edges are graduated into 1/4, 1/24, 1/32, and 1/64 of an inch
for ease in determining the pitch of threads on screws.
The back of the
center gage has a table giving the double depth of the threads in
thousandths of inch for each pitch.
This information is also useful in
determining the size of tap drills.
FIGURE 20.
CENTER GAGE.
(5) Thickness (Feeler) Gages.
(a) Thickness (feeler) gages (figure 21 on the following page) are
used to determine distances between two mating parts. The gages are made in
various shapes and sizes; usually 2 to 26 blades are grouped into one tool
and graduated in thousandths of an inch.
(b) Most thickness blades are straight, while others are bent at
the end at 45 degree and 90 degree angles. Some thickness gages are grouped
so that there are several short and several long blades together. Thickness
gages are also available in single blades and in strip form for specific
measurements.
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