I am building a small trunk for a military friend to put some belongings in. I have made legs out of ash hardwood and will make the sides out of 1/2” or 3/4” Baltic birch plywood. The legs are 1.5” thick by 2” wide. So since I’m drilling pockets in the plywood should I use coarse or fine thread going in the ash hardwood? And since I have thicker leg go with longer screw or stick with what is recommended for the plywood thickness I go with. Thanks for your help in advance, Mike
If it were mine i would use fine thread screws and go up one size longer. make sure you try it on scrap pieces first in case you need to drill a small hole in your hard wood to stop it from splitting
The best method of determine if you should use fine thread and or course thread it to consider what kind of wood are you driving the screws into. If you are driving the thread through a soft wood into a hard wood, then use fine thread. Use as long of a screw as possible without it exiting the back side as the more threads into the wood the stronger the joint.