BS 906-2:1972

This standard BS 906-2:1972 Specification for engineers' parallels. is classified in these ICS categories:

• 17.040.30 Measuring instruments

This British Standard applies to parallel steel blocks of the following grades and sizes:

Grade A accuracy. Sizes ¼ in × ½ in × 4 in to 1½ in × 3 in × 12 in.

Grade B accuracy. Sizes ¼ in × ½ in × 4 in to 2 in × 4 in × 16 in.

The parallels of Grade A accuracy are high precision parallels primarily intended for inspection; those of Grade B accuracy are primarily intended for general tool room work.

NOTE 1. The larger sizes of parallels may be made with a series of lightening holes drilled through their thickness, provided that the accuracy of the parallels is not thereby affected.

NOTE 2. The titles of the British Standards referred to in this standard are listed on page 2.

Seven sizes of Grade A parallels with cross section ¼ in x ½ in to 1½ in x 3 in and nine of Grade B parallels with cross sections ¼ in x ½ in to 2 in x 4 in. Material, standard sizes, finish, accuracy, protection and marking.