BS 1580-3 specifies limits of sizes, and tolerances, for single-start, clearance-fit unified screw threads, in inch units with diameters below 1/4 in.
BS 1580-3 specifies unified screw threads from Number 0 (0.060 in diameter) to Number 12 (0.216 in diameter), known as the “numbered sizes” in the following standard series:
- a coarse thread (UNC) series
- a fine thread (UNF) series
- for Number 12 threads, an extra fine (UNEF) 32 threads per inch diameter/pitch combination.
This part of BS 1580 is intended for use with BS 919-1 which specifies the corresponding screw gauges.
BS 1580-3 contains:
- Normative references
- Terms and definitions and symbols
- Thread profiles
- Diameter/pitch combinations
- Tolerance classes
- Tolerances, allowances and limits of size for uncoated threads
- Coated threads
- Designation of threads
BS 1580-3:2007 supersedes BS 1580-3:1965, which is withdrawn.