How far to countersink flush screws in spars?

[Gunther]

Hello to all. Should countersunk screws be absolutely flush to the spars or can the heads be slightly above the surface? If the heads must be flush, is it okay to countersink a little deeper with my Wicks 3 flute 100 degree countersink?

I am attaching the Root Wing Attach Assemblies (SNX-W11-06) to the spars and the plans call for Qty(3) flush screws to be used (MS24694-S58). The three holes have already been dimpled and countersunk with the prebuilt spar option but the heads of the screws are above the surface by about 0.020. Any other things to watch out for with this assembly?

Many thanks,
Gunther

[Ronsip]

I had the same issue on my pre-built spars. To get the screws flush I installed a MS24694-S58 screw without the attach assemble then tighten it down until it was flush. Then used the same screw for the other holes. It didn't take much to get them flush however still threw away the screw and nut.