BS 5590:1978 pdf free.Specification For Screw Thread Metric Series Measuring Cylinders.
BS 5590 relates to measuring cylinders for standard pitches of ISO metric threads given in BS 3643. The cylinders described are intended for use on threads of small helix angle, i.e. less than 5°.
Cylinders for measuring the pitch diameter of Unified, Whitworth form and B.A. threads are specified in Appendix C. (See BS 84, BS 93 and BS 1580 for details of these threads.)
4 Material and finish
4.1 Thread-measuring cylinders shall be made of steel and shall be hardened and tempered to avoid brittleness and breakages in use.
NOTE A hardness value of approximately 700 HV is recommended over the working length (see Figure 1).
4.2 The working surface shall have a lapped finish, free from any blemishes such as scratches, pits and rust stains.
5 Form and general dimensions
5.1 Form. The general form of the cylinders shall be as shown in Figure 1.
5.2 Overall length. Recommended approximate overall lengths, L, of screw thread measuring
cylinders are given in Table 1.
6 Accuracy
The requirements for accuracy shall apply over the working length as defined in 3.4.
6.1 Straightness. When a cylinder is held against a gauge block 9 mm wide by a cylindrical contact face exerting a force of 2.5 N (0.25 kgf approximately) and the cylinder is rotated, no light shall be visible immediately below the contact face between the thread-measuring cylinder and the gauge block (see Figure 2).
6.2 Uniformity of diameter. The diameter of the working length of the cylinder shall be uniform within 0.001 mm. Ffhjs value of 0.001 mm shall include any out-of-roundness of the cylinder (lobing) as detected by rotat.ing it in a ground screw thread, e.g. a gauge, having an included angle of 600, under a suitable measuring head.
6.3 Mean diameter. The mean diameter of each cylinder shall lie within a tolerance of ± 0.001 mm from the nominal size given in Table 2.BS 5590 pdf download.