BS 4827 discusses standards for ISO miniature screw threads. BS 4827 specifies the thread form, series, tolerance, and designation for the miniature screw threads. BS 4827 specifies requirements for ISO miniature screw threads from 0.30 mm to 1.4 mm in diameter with 60° ISO miniature screw thread form specified in ISO/R 1501 and conforms dimensionally with it.
The profiles and tolerance system for ISO miniature screw threads differ from the profile and tolerance system for ISO general purpose metric screw threads. In the range below 1.0 mm diameter the ISO miniature screw threads specified in BS 4827 form part of the complete series of the metric screw threads recommended by ISO.
BS 4827 on ISO miniature screw threads is useful for:
Miniature Screw Threads are used for wristwatches, optical equipment, electric instruments, etc. Miniature Screw Threads use the thread symbol prefix "S" for identification instead of using an "M" for metric threads.
BS 4827 explains the unified and metric thread tolerance designations. The metric system is more logical and gives the flexibility of applying different tolerances to different thread diameters, such as pitch diameter and internal thread minor diameter.
BS 4827 covers basic dimensions of standard diameter/pitch combinations and limits and tolerances for Internal threads (nuts) tolerance class 4H5, 4H6, 3G5, 3G6, 5H3. BS 4827 guidelines help you to ensure the reliability for the consumption of miniature screw threads metric series throughout the screw threads and fasteners applications. Following BS 4827, manufacturers can build trust in the use of miniature screw threads.