Cant find anything specific about this but when drilling for A4 rivets, should I start with  # 40 bit, cleco, then remove clecos and drill with #30 and cleco again, or can I simply drill with #30, cleco, then rivet. ? 

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Use #40 (A4) as pilot hole, then open to #30 (A5).  After which, debur, etch, and prime accordingly.  

Use #40 (A4) as pilot hole, then open to #30 (A5)

I agree to pilot with #40 and then expand to #30, but a #40 is for A3 (3/32") rivets and silver clecos and

a #30 is for A4 (1/8") rivets and copper clecos. (A5's are 5/32"-black clecos)



Thanks for the correction John

When I first began there was a document that gave general instructions.  Also there were numerous references to other documents that contained accepted procedures.  I would recommend a review of these.  It could prevent much rework.

Drill out first to #40, then cleco. Then delay enlarging to #30 for as along as is practical. My personal experience is that you want to delay doing anything that can not be undone for as long as possible. At the very least you save your self the time of drilling #30 holes if you discover that the #40's are not in the correct location.

always pilot holes first then step up to final size it makes a cleaner , and lessen the chances of drill bit walking on you. if you wanted to be real anal/ professional you can buy bits with pilots on them, ie double margin or core drills. that way the pilot on the bit will follow the pilot in the skin. lessens chances of holes moving on you.


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