BS 959:2008

Specification for internal micrometers (including stick micrometers). | Status: Confirmed, Current

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:

1. 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;
2. 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.