[FlyBoy8]

For some reason I have a difficult time getting consistent results with my countersink even after carefully adjusting it on scrap.

The first CS I did on the spar seems to be too deep, but it does measure at .375 which is supposedly OK. I sent an email and pic to Vans but they haven't responded yet (probably all at Air Venture where I wish I was).

 

[FlyBoy8]

I just bought a new digital caliper and it says the CS is .382

 

[DaAV8R]

Countersinks

I doubt if a few thousands on a couple of holes will make the wing fall off

I find I get more consistent depths if I drill about 80% of the way, stop and blow the slivers out of the cage and then finish off the countersink. Not sure why that is but it is my experience. It also give me a chance to view the hole with a little meat left and make certain I am straight.

After your eye gets calibrated you can just about achieve the correct depth by eye alone.

 

[Andrew M]

Backup

I clamped a piece of thick material behind the web and worked all those holes in assembly with it to hold the pilot steady. Helped a lot.

 

[RV7]

Use a backing piece for the the pilot as Andrew mentioned. It allows for accurate and consistent results.