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THE THIMBLE
• The Thimble rotates about the Sleeve and moves in and out as it is turned
(FIG 1)
.
• One complete rotation of the thimble is also equal to the smallest divisions of the Sleeve which,
of course, is 0.025” or 1/40” (1 40th of an inch).
• The Thimble is divided into five equal segments, each one with a “long” line and numbered
from “0” to “5”, “10”,”20” and back to “0”. Each of these numbered lines represents 0.005”
• Every one of the “medium” segments equals 0.001” or 1/10” (1 10th of an inch).
• The shortest lines between the “medium” 0.001” length lines represent 1/2 of 0.001 (0.0005”)
and are for approximation only.
EXAMPLE
In this example, a worn automotive valve stem is used to illustrate the sequence of determining a final
dimension of a part
(FIG 2)
.
• The position of the Thimble edge over the Sleeve markings shows 0.300 + 2 additional marks
equaling 0.025 each which equals 0.050 for 0.350”.
• The marks on the indicted on the Thimble in relation to the horizontal line on the Sleeve is
showing 0.020 + one additional mark of 0.001 for a final dimension total of 0.371”.
FIG. 2
0.30
0”
0.350
”
0.300
+ 0.050
+ 0.020
+ 0.001
= 0.371
Final Dimension