Course or Fine screws in plywood?

[Justin]

Hi All,

I am working on a project using 3/4 oak sanded plywood.  Thinking "oak" I used 1 1/4in course screws in one joint as a test.  2 out of the three felt strong, the one that didn't spun out of the thread and became useless.  Should I have used a course screw or a lighter clutch setting?

[Jay Boutwell]

Justin, I been building cabinets using 3/4" plywood and 1 1/4' fine thread screws for better than 20 years and have had no problems with screw pull out or failing joints.  I realize that the plywood cores are being made with a less quality of wood with much of it being made of cheap soft core, unless you are using a quality furniture grade plywood.  Some of the  plywood  being sold by home centeres are not the best grade of materials and wome are better that others.  Some of the problems I have seen in the lower grades is soft core with tendacy to split within the core.  Some problems have been voids in the core and very thin top veneersas well as dry glue spots in the core sheets leaving loose bonds in the plywood.  Something I always do is to add some glue to the screw thread as well as in the joint surfaces.    I hope this helps you with your problem as is is never fun building something only to have a bad joints as your reward for your hard work and never easy on the pocketbook either.  Have a good day.

[Justin]

Thanks Bravo and Jay, I will let you know how the next couple of joints turn out.