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#12 countersink

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Barneybc12d

Well Known Member
I am working on the aileron hinge bracket. Plans call for a #12 countersink. I have the tool, but no #12 flathead to gauge the depth. Am I missing a part or is this something they expect a first time builder to have on hand? Will a hardware store have one with the same dimensions or do I need to order a AN fastener to complete this step? I have a #10 screw but am afraid to countersink a little deeper than the 10 hoping it will be right for the 12.
 
I think, not certain, that the #12 refers to the pilot diameter. If so it would be a hair larger than 3/16". If the hole diameter is 3/16" and/or the fastener is, then you'd know for sure that that's what they mean, and a countersink for that will work.

Dave
RV-3B, still on the fuel tanks.
 
David Paule said:
I think, not certain, that the #12 refers to the pilot diameter. If so it would be a hair larger than 3/16". If the hole diameter is 3/16" and/or the fastener is, then you'd know for sure that that's what they mean, and a countersink for that will work.

Dave
RV-3B, still on the fuel tanks.
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I am sure that the pilot diameter is a #12, but my issue is how deep to countersink.
 
How many clicks.

If a #10 is (x) clicks deeper than a #8, would a # 12 be the same number of clicks deeper than a #10?
 
Barneybc12d said:
If a #10 is (x) clicks deeper than a #8, would a # 12 be the same number of clicks deeper than a #10?
Click to expand...

I wouldn't count on it.

I'm not building a -14, but surely there is some indication somewhere in the plans that shows what goes in that hole. Whatever it is, I would think it should be in the wing kit.
 
The part called out (AN509-10R25) is in bag 3017 of the wing kit. It fits a #12 hole. It screws into the 10-32 nut plate you will be installing.
 
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I'm not building a 14 either...

But on the 7 I just drilled a #12 hole and countersunk with a #12 counter sink for a #10 counter sunk screw, it goes thru the skin and lower longeron to hold the angle on the backside for the tank bracket. I'm gonna guess that you'll be putting a #10 screw I that hole so that's what I'd be looking for on the plans.
 
n982sx said:
The part called out (AN509-10R25) is in bag 3017 of the wing kit. It fits a #12 hole. It screws into the 10-32 nut plate you will be installing.
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Thanks Bob

The callout was in the next section, I didn't dig deep enough.
I was focused on a #12 screw going into a #12 hole.

Barney
 
MeAndMyToys said:
But on the 7 I just drilled a #12 hole and countersunk with a #12 counter sink for a #10 counter sunk screw, it goes thru the skin and lower longeron to hold the angle on the backside for the tank bracket. I'm gonna guess that you'll be putting a #10 screw I that hole so that's what I'd be looking for on the plans.
Click to expand...

Thanks for the reply, I found the callout, you are correct, it is for a #10.
 
Barneybc12d said:
Thanks Bob

The callout was in the next section, I didn't dig deep enough.
I was focused on a #12 screw going into a #12 hole.

Barney
Click to expand...

The actual size number of a screw has no direct correlation to the size number of the hole.
For a # 6 screw we typically use a #27 hole.
For a # 8 screw we typically use a # 19 hole.
For a #10 screw we use a # 12 hole (which is the same as what is used for an AN3 bolt BTW).
The fact that for that size screw, the numbers just happen to be close together is probably what threw you off.
The number value labeled on countersink cutters is always the size hole the pilot will fit (#40 countersink, for a # 40 hole for a 3/32 size rivet), not the size fastener it is used for.
 
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