BS 3777:1964

This standard BS 3777:1964 Specification for screw thread measuring cylinders is classified in these ICS categories:

• 17.040.30 Measuring instruments

This British Standard relates to two grades of screw thread measuring cylinders intended for use in checking external screw threads by means of pitch diameter measuring machines.

NOTE For a full description of this well established method of measuring the effective diameter of an external screw thread when using thread measuring cylinders, and also for an explanation of the P value used in this measurement, see “Notes on Applied Science No.1” issued by the Department of Scientific and Industrial Research and entitled “Gauging and Measuring Screw Threads”, published by Her Majesty’s Stationery Office.

The standard comprises two parts:

Part 1 gives the bases for the diametral tolerances of Grade A and Grade B screw thread measuring cylinders and the relative merits of the two grades.

Part 2 gives the complete specification for both grades of cylinders suitable for the forms and pitches of screw threads shown in Table 1.

Grade A (pitch-line) and Grade B (grouped) measuring cylinders for checking external screw threads of Unified and ISO inch, Whitworth, B.A. and ISO metric form by means of pitch diameter measuring machines. Bases for the diametral tolerances. Relative merits of grades A and B. Measuring ranges, material and finish, form and general dimensions, accuracy and identification; tables of nominal diameters and associated P values for Grade A cylinders; limits of size for Grade B cylinders.