Adjusting Micrometer Caliper to Work.

graduations should be noted to avoid confusion:

(a) The pitch of the micrometer screw is 0.5 mm. One revolution

of the spindle advances or withdraws the screw a distance equal to 0.5 mm.

(b) The barrel is graduated in millimeters from 0 to 25; it takes

two revolutions of the spindle to move 1 mm.

(c) The thimble is graduated in 50 divisions with every fifth line

being numbered.

(d) Rotating the thimble from one graduation to the next moves the

spindle 1/50 of 0.5 mm, or 1/100 mm. Two graduations equal 2/100 mm, and so

forth.

(3) Adjusting Micrometer Caliper to Work.

(a) Figure 193, view A, on the following page, shows the proper

way to hold a micrometer caliper in checking a small part. Hold the part in

one hand. Hold the micrometer in the other hand so that the thimble rests

between the thumb and the forefinger.

The third finger is then in a

position to hold the frame against the palm of the hand.

The frame is

supported in this manner which makes it easy to guide the work over the

anvil. The thumb and forefinger are in position to turn the thimble, either

directly or through the ratchet, and move the spindle over against the work.

(b) On larger work, it is necessary to have the work stationary

and positioned to permit access to the micrometer.

The proper method of

holding a micrometer when checking a part too large to be held in one hand

is shown in figure 193, view B. The frame is held by one hand to position

it and to locate it square to the measured surface. The other hand operates

the thimble, either directly or through the ratchet.

A large flat part

should be checked in several places to determine the amount of variation.

(c) To gage a shaft as shown in figure 193, view C, the frame is

held by one hand while the thimble is operated by the other. In gaging a

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