I suggest the coated screws for heavy work. You can buy a small plastic
box of them for not much. They won't start to corrode in the
hole and grab with thousands of bits of steel and Oxides.

Often for Concrete or heavy work, they are strong. Cheap price in the
long run.

And wax is a good lube as well as it melts and fills voids in the
surface of screws.

Martin

On 5/31/2015 6:43 PM, DJ Delorie wrote:

Are you pre-drilling for the screw holes? I think the fact that you
need an impact driver tells me something's wrong. A properly
pre-drilled hole should make it easy to install and remove the screw,
without compromising strength (and might be stronger).

I've also started using McFeely's screws (or other "real" screws) where
strength counts, I've broken many a box-store screw, but the McFeely's
screws will destroy a piece of oak (or stall my big hammer drill) before
they break.

(And yes, wax is good. Never use soap on a screw.)