PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 2
Step 2. Turn the thimble of the outside micrometer with the thumb and the
forefinger until you feel the inside tool legs lightly contact the anvil and
the spindle of the outside micrometer.
Hold the tips of the inside tool
legs parallel to the axis of the outside micrometer spindle.
Step 3. The outside micrometer will be accurately set when the inside tool
will just pass between the anvil and the spindle of the outside micrometer
on its own weight.
d.
Depth Micrometer. A depth micrometer is used to measure the depth of
holes, slots, counterbores, recesses, and the distance from a surface to
some recessed part. This type of micrometer is read exactly opposite to the
method used to read an outside micrometer. The zero is located toward the
closed end of the thimble. The measurement is read in reverse and increases
in amount (depth) as the thimble moves toward the base of the instrument.
The extension rods come either round or flat (blade like) to permit
measuring a narrow, deep recess or groove.
e.
Thread Micrometers.
(1) Thread micrometers are used to measure the pitch diameter of
threads.
They are graduated and read in the same manner as ordinary
micrometers. However, the anvil and spindle are ground to the shape of a
thread.
(2) Thread micrometers are used to measure the depth of threads that
have an included angle of 60ƒ.
The measurement obtained represents the
pitch diameter of the thread.
They are available in sizes that measure
pitch diameters up to 2 inches. Each micrometer has a given range of the
number of threads per inch that can be measured correctly.
f.
Ball Micrometer.
This type of micrometer has a rounded anvil and a
flat spindle.
It can be used to check the wall thickness of cylinders,
sleeves, rings, and other parts that have a hole bored in a piece of
material. The rounded anvil is placed inside the hole and the spindle is
brought in contact with the outside diameter.
Ball attachments are
available to fit over the anvil of regular outside micrometers. When these
attachments are used, compensation for the diameter of the ball must be
added to the regular reading.
66
Previous Page
