2b 2nd end thread class 36 2nd end thread quantity per inch two sets of thds on boss end 0.375-24 unf 2a rh 0.219 in. lg; 0.562-32 uns 2a rh 0.219 in. lg uns 2nd end thread series
2a 2nd end thread class 12 2nd end thread quantity per inch features must conform to special quality control provisions for (hx) propulsion un 2nd end thread series