J

jchang10

Well Known Member
Hi Everyone,

I just wanted to verify my countersinking technique before diving in.

Should I adjust the countersinking tool so that a flush rivet sits just slightly up above the surface, knowing that the rivet will get squeezed flush with the skin when riveted?

IE, i should err on the side of countersinking too little than too much. THe deper the countersink hole is, the rivet may risk sitting too lose in its hole?

Thanks,
Jae
 
Jae, what I did was pick up a 3'x1"x1/8" piece of AL bar at OSH for testing my CS depth. When I need to countersink, I just drill a several holes in my test piece and then test my countersink depth on them, making adjustments before I CS pricey aircraft parts.

When I started, I must have countersunk 30-40 holes in the scrap before I got the courage to touch the kit with the CS. ;)

One more thing... try to countersink with something behind the piece such as a piece of wood or similar. You should drill the wood with a hole to accept the pilot of the countersink cutter, as this will help keep your holes nice and round. If you don't have something to guide the pilot, the cutter can wander and you can end up with an egg shaped countersink.
 
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mark countersink

I have been thinking of marking the side of my countersink with two different colored dots for each type of rivet or screw we use so that I can just match the dots and be ready to go rather than doing the creap technique that is the logical alternative. Does anyone see a reason this wouldn't work?

Antony
 
I thought about doing this too. Since it could be off by 360-degree increments on the countersink gauge and I would still want to test the depth beforehand, I decided it really wouldn't do anything other than give me a place to start my testing.
 
Thanks again

Everone... thanks for the excellent tips. i should have tested on some scrap like you said. oh well, i will see what effect having too deep a countersunk hole does. :(

i was just caught off guard by the variability of the depth based on several factors: downward pressure, alignment, and sensitivity of the cage. i thought 90deg turns were fine enough, but i see i should use finer increments.

jae
 
Drill press

In addition to using the AL scrap to test drill, I use the drill press to countersink if there's any way possible. For me, the drill press is much more consistent than a hand held drill when c'sinking. I use a piece of scrap particle board with a 1" center hole clamped to the drill press table as my backing surface.
 
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