Your in your woodshop and have completed cutting out the pieces for the cabinet your building. All of the panels have been sanded down and you are ready to assemble them. You have dry fitted the pieces together and now have glued and clamped them with bar and pipe clamps. After fastening them together you realize that the cabinet is out of square. A clamping square can help prevent this problem from happening.
Using a framing square it is fairly easy to check if a joint is square. However, holding the square against the panels, checking that the panels are still square and then also driving fasteners just doesn’t work. You only have two hands. And a framing square is not designed to be clamped to the panels while the fasteners are being driven.
A clamping square is a piece of metal that has been milled to have a 90 degree angle where the legs meet. A good clamping square is made out of thick aluminum, light weight and can with stand the rigors of being clamped to panels.
You want to look for clamping squares that are 3/4 inch thick and have at least 3/4 inch wide legs, preferably one inch thick legs. I prefer at least six long legs. This provides plenty of clamping space along the length of the leg.
Some of the better clamping squares have counter bored holes on each leg that will allow the clamping corner to be mounted on a jig or a work bench. This is especially useful for repetitive assemblies.
How to use a clamping square?
Place the clamping square in the corner it can be either the inside or outside of the corner. Use any clamps you have handy to clamp the clamping square to the panel. Heavy duty clamps are not required and may even make it harder to use the clamping square. This is because of the additional weight of the clamps and their size will make it more difficult to handle the pieces while clamped together. Instead use smaller speed clamps such as quick grip or similar.
Clamp a clamping square at both the top and bottom of the joint. Fasten the panels together and then remove the clamps.
Clamping squares work best when using pocket screws to attach the panels. With all of the force required to drive the screws into the opposite panel, there is a very good chance that the panels will slip just a bit out of square. However, when using clamping squares, the panels will stay nice and square even while the fasteners are driven in.
