tkatc

tkatc

Well Known Member
Maybe I should already know this but I'm a bit tired and need help.

I am machine countersinking the lower longerons to accept the skin dimples. #30 holes use a #30 countersink. Easy enough. But now I have to countersink for an AN509-8R8 screw. The hole is I'm guessing a 12 or 19 so my #30 countersink won't work very well in the larger hole even though all my countersinks are 100 degrees.

Please help my tired brain...
 
Thanks for the links guys! The cutter will actually have a #19 printed on the side as the pilot size is a #19 wire size. This is the clearance hole size for a number eight screw.
 
If you drill the hole at #20, and then use the #20 piloted countersink to the proper depth for the screw, you can then drill/ream the hole to #19 if needed.

Just drill the first hole to the same size as your countersink pilot.
 
You must log in or register to reply here.