The Micrometer - 8: Sizes
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WARNING: Machine tools present a safety hazard. Improper operation can result in severe injury. These topics are for non-laboratory study only and are not to be used in conjunction with the operation of any tool or machine described herein. Never use a machine tool without the supervision of a qualified instructor.
As mentioned in the note at the bottom of the previous page micrometers are available in many sizes. The basic OD mic is the one inch mic which ranges in size from 0" to 1" (shown below)The OD mic is available in one inch increments after the first inch. For example the next size up from the one inch micrometer is the two inch which ranges in size from 1.000" to 2.000 inch. The next size after that would be the three inch which ranges in size from 2.000" to 3.000". The first three sizes are very common and are available in sets as shown below.
Note the "standards" shown in the lower left corner of the wooden box set. Since the anvil and spindle cannot be screwed together to check and adjust accuracy (as shown in page 6) the manufacturer of the micrometer set provides a length of hardened and precision ground steel to use as a gage for the two inch and three inch micrometers. They are called "standards" and are accurately ground to a tolerance of less than .00005"
Larger sets are available. The set shown on the right ranges from 0-1" to 11-12". Each micrometer has a standard too.
When micrometers become ery large they are offered in sets like the one shown below. In this set the anvil is interchangeable and has six of them in one inch increments. In effect this allows for a range of 12" to 18". Each anvil size has a corresponding standard for setting accuracy.

Some micrometer sets can measure as large as 80" in diameter.

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label: micrometer, history, anvil, thimble, spindle, frame, barrel, ratchet, adjustment, holding, handling, reading, vernier