6 threaded holes 0.250-28 unf 2b 0.500 in. deep in hex equally spaced on a 3.812 in. bcd N1 outside hexagon or octagon (partial or full thread optional)
Used on sikorsky cargo transport helicopter, ch-54a and ch-54b, also f-18 aircraft. 3b internal thread class right-hand internal cap drilledfor safety chain anodize surface treated cap, tube, flared unf internal thread series
Used on sikorsky model ch-54a and ch-54b cargo transport helicopter. 3a 2nd end thread class 12 1st end thread quantity per inch anodize surface treated unj 1st end thread series
