The ultimate test of squareness

Tuesday, December 4, 2007 | Reader Comments | How-To

by John Lucas, Professor of Perpendicularity

Having an engineer's square to check your saw squareness is fine but not the ultimate test. I mentioned in my last column, that the real test is in the woodwork — does that fourth corner come together without excessive clamping?

For me, making a small cube with mitered sides and corners is a true test of both the saw setup and my procedures.

I have just posted two pages on my website ( showing Elena and me testing our methods by building a cube. If you think making a frame with 4 mitered corners is hard, try this test of cutting all 6 sides and having them fit together without clamps and without gaps in the corners. When you can do that, your system is right on and you can feel better about building cabinets and boxes of any sort.

John Lucas John Lucas
01 Elena cuts the full length board using the long guide rail. This is the “with the grain”, parallel cut. 02 For the crosscut (square), I have set up a temporary fence to make the cuts faster and more accurate. I am using this on the worktable rather than use one of the MFT's.
John Lucas John Lucas
03 I now have all 6 sides cut and ready to assemble. By stacking them front to back in pairs as I have here, I can get a quick glimpse of how accurate the “parallel” cuts were. 04 Rather than put the sides in clamps for the glue up, I am using duct tape to “hinge” the sides. All I have to do is lay the corner edges tight against the mating side and fold up the side.

When all four sides were together with tape, I simply added the top and bottom sides and added more tape. When the CA glue sets, I can remove the tape and inspect the cube, but I can tell already that this cube is perfect. Is the time I took to make the test worth it? It is to me. I like to know that I can build cabinets, shelves — anything with square corners and parallel sides.

Thanks for the great demonstration, John!

John Lucas

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