Reply To: Checking My Combo Sqaure
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Another way to check for a square angle dates back to the ancient Egyptians and is perhaps even older, but the Egyptians left evidence:
If you make a triangle with side lengths of 5,4 and 3 units (inch, millimeter, parsecs, whatever you like), the angle between the line with 3 and 4 units will ALWAYS be 90° – square.
So, when you measure 3″ on one side of your square (handle) and 4″ on the other side (ruler), the distance between these points should be exactly 5″.
Why? Because 3² + 4² = 5² (9 + 16 = 25), and Pythagoras showed, that a² + b² = c² on all triangles with a square angle between line a and b.
Of course, this leaves you with the question, how accurately you can measure the distance, and how accurate is your ruler. It is always a chicken-egg problem.
So here is one suggestion: How precise is your working with chisels, saws, planes etc.? does 1/32″ really matter on a length of 10″? Paul often says “we strive for perfection”, which also means, “we aren’t perfect yet”.
Dieter