One of the things in woodworking that I am very passionate about are squares. In my early days of woodworking, unbeknownst to me, a couple of my squares were off by square by quite a bit and were causing me no end to problems and frustrations. I cannot tell you what a frustrating time that was for me. It wasn't until I purchased a decent quality steel square that I realized that not all squares are necessarily square.

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Once I realized that my problem all along was probably my squares and not my machinery or the way I was setting it up, a whole new world opened for me.

It was a huge relief to finally figure out that my problems all along were a couple of $20 (or so) squares and not my much more expensive table saw and jointer, nor was it the way I was aligning wood for gluing ... faulty squares, as simple as that.

Here were the culprits ...

Combination square

Checking Squares
So the first thing I wanted to do was to figure out which squares were accurate and which were off. It's a simple process when you know how. I prefer to have a sheet of plywood or MDF with a factory edge that is at least 3 feet square. This way I can check all my squares and still end up with some good wood to use later.

Lay your square with short side along the factory edge and the long side laying on the plywood. On the INSIDE of the square make a fine thin line with a sharp pencil at the to and without moving the square, another one near the bottom, also on the inside. 

Framing square

Flip the square over and align the inside with the top pencil mark you just made and see if it aligns with the bottom one. If it does, your square is good, if not, with some squares you can re-align them, particularly if they are single width. If they have thick handles and are out of alignment, I know of no way to re-align them.

To Align Squares
Squares that are "pinched" ... that is the arms are too close to one another, using a simple punch near the crotch of the square will often expand the metal just enough to re-align those 2 arms. It often does not take much some go gentle, you don't want to overdo it.
For arms that are apart or obtuse the same technique using a small round punch but this time toward the outer point where the arms come together. Driving a punch in here will tend to expand the metal a very small amount and push the arms together just enough to align them at 90 degrees to one another. Again do this one hammered punch at a time, check then repeat as need.  

aligning a combination square

Engineers Square
My days of drafting plans by hand taught me the value of using Engineers Squares. They aren't really expensive and I have been using them for over 40 years. You can also use these to check you square and to set up your machinery with as well. I often use my engineers square when setting 45-degree angle on my table saw, nothing is more accurate.

Combination square with engineers square

In my early days of woodworking, I underestimated the value of having accurate squares and how much difference that made to how my wood projects aligned and fit together. It was a valuable lesson and has served me well to know how accurate my squares are and to be able to set them so they are dead accurate.

Copyright Colin Knecht


Checking Squares for Accuracy