Brief Description: Countersink Setup for AN426-4 rivets
I had to replace my #40 countersink, and reset the rivet-only setting to account for the slightly longer body of the bit. Once I did that the rest of the settings (see the Tools section, July 6, 2014) fell right in place.
After countersinking all of the #40 holes in the longerons for attaching the side skins, I still had the 7 forward most holes that are #30. With a bit of experimentation, I discovered that the setting for an AN426-4 rivet is 9 "clicks" LESS THAN two full turns deeper than for an AN426-3 rivet. Just as with the -3 shank size, the countersink for a dimple in 0.032 sheet using a standard die set is 7 "clicks" deeper than for a rivet only.