PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 2
Blade Micrometer. A blade micrometer has an anvil and a spindle that
are thin and flat.
The spindle does not rotate.
This micrometer is
especially useful in measuring the depth of narrow grooves, such as an O-
A groove micrometer looks like an inside
micrometer with two flat disks. The distance between the disks increases as
the thimble on the micrometer is turned. It is used to measure the width of
grooves or recesses on either the outside or the inside diameter. The width
of an internal O-ring groove is an excellent example.
Care of Micrometers.
The micrometer is one of the most used, and
often one of the most abused, precision instruments in the shops. Careful
observation of the do's and don'ts listed below will enable machinists to
(1) Always stop the workpiece before taking a measurement.
measure moving parts because the micrometer may get caught in the rotating
workpiece and be severely damaged.
(2) Always open a micrometer by holding the frame with one hand and
turning the knurled sleeve or thimble with the other hand.
Never open a
micrometer by twirling the frame, because such practice will put unnecessary
strain on the instrument and cause excessive wear of the threads.
(3) Apply only moderate force to the knurled thimble when taking a
measurement. Always use the friction slip ratchet if there is one on the
instrument. Too much pressure on the knurled sleeve will not only result in
an inaccurate reading, but may also cause the frame to spring, forcing the
measuring surfaces out of line.
(4) When a micrometer is not in use, place it where it is not likely
to be dropped.
Dropping a micrometer can cause the frame to spring; if
dropped, the instrument should be checked for accuracy.
(5) Before a micrometer is returned to storage, the spindle should be
backed away from the anvil. Wipe all exterior surfaces with a clean, soft
cloth, and coat the surfaces with a light oil. Do