2b thread class 32 thread quantity per inch has groove beneath head 0.190 in. dia, 0.060 in. wide, ctr hole countersunk at top, 0.190 in. dia, 90.0 deg flange unc thread series
3b thread class 20 thread quantity per inch has lockwire hole 0.062 in. from top edge, 0.046 in. dia drilled 0.420 in. from center axis passivate surface treated flange unjf thread series