TB 9-5210-204-24
c. Rotate thimble several times along full length of thread range to determine if
roughness, binding, or irregularities occur. If necessary, disassemble thimble and spindle
from barrel and check for foreign matter or lack of lubricant.
NOTE
The method to be used is determined by the type of micrometer
ratchet thimble, a learned "feel" must be used to ensure a
consistent, accurate measurement. Using index finger and
thumb rotate the thimble until the anvil and spindle clamp the
standard (device being measured) slightly; the fingers must
then slip so no additional clamping will occur. If micrometer is
a clutch type (ratchet or free spin), after making contact with
standard, continue turning to turn until thimble begins to
click or turn freely. Readings must be repeatable.
d. If necessary, clean thimble, anvil and spindle and apply a small quantity of instrument oil.
a. Performance Check
NOTE
Parallelism measurements are not required for ball-anvil
tubing or other types of micrometers that do not have a flat
anvil and flat spindle opposed and parallel to one another.
NOTE
If TI basic length is too great to permit direct contact with both
sides of ball micrometer tester, proceed to technique (7) below.
(1) If contact is possible, perform parallelism tests for TIs with a 0 to 1 inch range as
listed in (2) through (6) below.
(2) Position ball micrometer tester small ball (0.1875 in.) between the TI, anvil and
spindle measuring faces at point A as shown in figure 1.