[skydiverlv]

The T-407 backing ring is required countersunk for attachment to T1202 forward
tank bulkhead which is required dimpled at same locations to be mated together
with 426AD3-4 rivets. I have countersunk T407 with 100 degree bit and the ring does not mate well with the dimples. Will T407 need 120 degree countersink holes to mate properly?

 

[Mich48041]

Will T407 need 120 degree countersink holes to mate properly?

I do not think so. I countersunk the T-407 deeper until the two parts fit together without a space between them.
Joe Gores

 

[skydiverlv]

I do not think so. I countersunk the T-407 deeper until the two parts fit together without a space between them.
Joe Gores

Sounds like a plan, Joe. Thanks