1 Scope
This standard specifies requirements for internal micrometers comprising a measuring
head, extension rods with or without spacing collars, and, in the smaller sizes, a
handle.
Provision is made for three sizes of measuring heads, in both metric and inch units,
as shown in Table 1 and Table 2.
NOTE Attention is drawn to the fact that metric dimensions are not necessarily direct conversions of the imperial dimensions.
Table 1
—
Measuring heads — metric measurements
|
Size of head
|
Length of graduated scale on barrel
|
Usual ranges of the instrument when used with extension rods
|
|---|---|---|
|
mm
|
mm
|
|
| Size 1 | 5 or 6.5 | 25-50 |
| Size 2 | 10 or 13 | 50-150 |
| 50-200 | ||
| 50-300 | ||
| Size 3 | 25 | 200+ |
Table 2
—
Measuring heads — inch measurements
|
Size of head
|
Length of graduated scale on barrel
|
Usual ranges of the instrument when used with extension rods
|
|---|---|---|
|
in
|
in
|
|
| Size 1 | ¼ | 1-2 |
| Size 2 | ½ or 1 | 2-6 |
| 2-8 | ||
| 2-12 | ||
| Size 3 | 1 | 8+ |
This standard also covers stick micrometers, which are designed for the measurement
of longer internal lengths, and comprise the following parts:
-
a) a 150 mm or 300 mm or 6 in or 12 in micrometer unit, fitted with a micrometer of 25 mm or 1 in range, and having rounded terminal faces;
-
b) a series of extension rods which, together with the micrometer unit, permit a continuous range of measurement up to the maximum length required.
Annex A gives a method of test for the accuracy of internal micrometer readings.