BA (British Association) Threads are used for fine fastening purpose especially in instruments.
Specification :
Basic Dimensions – BS 93 : 1951 & Gauging Practice – BS 919 Part II : 2007.
Manufacturing Range :
Thread Plug Gauges, Thread Ring Gauges, Check Plug & Wear Check Plug Gauges for sizes 2, 3, 4, 5, 6, 7