I am an experienced carpenter and do some cabinetry.
I just purchased the Kreg 4 jig. I wanted to test the jig by building a simple box with some scrap 3/4" paint-grade plywood and 1 1/4" screws to bind the box sides. I have set the depth gauge and stop block correctly for my wood pieces and for the drill.
When I screwed my side panels together I got some splitting of the wood. Now I was lazy and used 1 1/4 coarse drywall screws. I'm figuring that caused some wood splitting.
Could I use SPAX screws instead of Kreg Screws?
Jeff, The screws are most likely the problem. Kreg joinery is designed to be done with Kreg screws. I have used Kreg products for a number of years and had no problems if used as designed. Get the Kreg screws and get the kreg results. Good luck
A person should never use sheet rock or dry wall screws on anything except to attach drywall to framing. The Kreg jig uses a bit that drills a flat bottom hole with a pilot hole to guide the screws directions into the receiving wood member. Dry wall screws are a bugle shank screw of which enters the pilot hole and then acts like a wedge that will split the pocket hole. The difference is that the kreg screw is pan head type head (flat) that screws up to the flat bottom hole and tightens the joint using the flat portion of the bored hole.
Using a screw with a flat head bottom will work however I would not do that. Spax screws are construction screws and most that I have seen are also bugle head.
I see that you do some cabinetry and I do hope you do not install cabinets on the wall with dry wall screws. If you do please read my post on cabinet hanging and what happens when you hang a cabinet with improper screws. Dry wall screws have tensile strength but brittle with sheer strength.
This was a scrap project and I never use drywall for finished cabinetry projects. I did not have any Kreg screws available so I used a coarse drywall 1 1/4" screw.
I use SPAX lumber screws or wood screws for cabinetry or shelving projects.
FWIW, I retried the first project with SPAX 1 1/4" self drilling wood screws and the joint held perfectly. No splitting and easy to drive with a TORX like bit.
I will buy some Kreg screws now - but SPAX did a great job.