I'm planning a workbench using mortise and tenon joinery on the base. I'm pretty new to woodworking, so this is a learning process. I'm planning on starting with Douglas fir 4x4's and I'm trying to figure out the size of the mortises and tenons. A few Google searches have yielded some general rules. So, let's say I've milled the lumber to 3x3. Following a rule that tenons should be 1/3 the thickness of the mortised piece, the tenon should be 1 inch thick. A similar rule (2/3 the thickness of the mortised piece) leads to a 2 inch long tenon. But a rule from the same source indicated a width of the tenon should be 5 times the thickness, which would be 5 inches. Obviously, that's impossible with 3x3 stock. So, how wide should the tenon be? Should it just be the entire width of the stock? And as long as I'm asking, should I use blind or through tenons? If it makes a difference, I'll probably use dowels through the tenons.
As I said, I'm new to this, so feel free to correct my assumptions above if you think they aren't the way to go.
Cheers.