TM 9-243
TYPES AND USES - Continued
TRAMMELS
The trammel measures distances beyond the range of
calipers. The instrument consists of a rod or beam (1) to
which trams (2) are clamped. The trams (2) carry
chucks (3). The trammel can also be used as a divider
by changing the points.
READING A VERNIER CALIPER
To read a vernier caliper, you must be able to under-
rule (1) is graduated in 0.025 of an inch. Every fourth
division (2) (representing a tenth of an inch) is num-
stand both the steel rule and vernier scales. The steel
bered.
The vernier scale (3) is divided into 25 parts and num-
bered 0, 5, 10, 15, 20, and 25. These 25 parts are equal
to 24 parts on the steel rule (1). The difference between
the width of one of the 25 spaces on the vernier scale (3)
and one of the 24 spaces on the steel rule (1) is 1/1000
of an inch.
Read the measurement as shown above.
Read the number of whole
inches on the top scale (1) to
the left of the vernier zero
index (4) and record
. . . . . . . . . . . . . . . . . 1.000 inch
zero index (4) and record
Read the number of tenths (5)
. . . . . . . . . . . .0.400 inch
Read the number of twenty-fifths (6)
to the left of the vernier
between the tenths mark(5) and
the zero index (4)
and record
. . . . . . . . . . . . . . . . .3 x .025 = .075 inch
Read the highest line on the
vernier scale (3) which lines up
with the lines on the top
scale (7) and record. (Remember
1/25 = .001 inch) . . . . . . . . . . 11/25 or 0.011 inch
TOTAL
1.486 inches
6-4
