Just how do you attach table legs, so your table is secure and level? Do you have a table that is wobbly?
There are quite a few reasons why a table can be wobbly. A table with the legs attached directly to the top without any aprons or runners relies exactly on the top to be very stiff. The question is how big is your table? How thick is the plywood used? Before you attached the plywood, does it easily wobble?
Does it have aprons or runners? Large tables with legs attached directly to the top usually have a very solid top.
Are the feet of the table level on the floor? Can you even out or stabilize the table with pieces of paper under some of its legs? If that is the case, the legs might not have the same lengths or the floor isn't level. First thing to do is; you can sand the bottom of the longer legs if they’re wooden. Or you can glue things on if necessary. If it’s the floor that is not level, you most likely don’t want to modify the table eternally just to fit in, but you may insert some temporary shims.
The standard way to make a table stable is in fact not to rely on the top itself to supply the firmness just to hold the legs parallel, but to add aprons. Like so: The aprons can be attached to the legs in various ways: dowels, pocket screws, mortise and tenon, visible screws, and any sorts of bracket type hardware stuffs that comes into mind. The apron holds each pair of legs equivalently. The only structural purpose of the top apart from the realistic function of keeping the things you set on the table from falling to the floor is to keep aprons parallel.
Read more on this at ‘Woodgears’ website and see detailed photos for their method and detailed instructions on how to attach table legs.