On Jun 23, 9:46 pm, Ray K wrote:

Yes, the screws I used for testing have flat heads, somewhat like sheet
rock screws. I could countersink the holes to prevent this problem.
Wouldn't I also have to countersink for pan head screws to get them
flush with the lumber?

A countersink is tapered, such as used for drywall and flat head
screws, and it creates a wedging action as the screw is driven home.
That is what's causing the wood to split. A counterbore for a pan
head screw would have a flat bottom. That provides a clamping action
and won't wedge the grain apart.
http://en.wikipedia.org/wiki/Countersink
http://en.wikipedia.org/wiki/Counterbore

You could also use stainless steel finish washers and eliminate the
counterbore. The flat head screw would still sit proud of the
surface, but it might satisfy your aesthetic requirements.
http://www.jamestowndistributors.com...Finish+Washers

R