How Square is Your Square?
A common question that comes up in woodworking forums is “How do I know if my square is really square?”. Without access to an equipped metrology lab, this question can be rather difficult to answer with great accuracy, but we can come close enough to know if we have a serious problem with a square.
The most common method for checking if a square is a true 90 degrees involves using, what I call, the Pencil-Line-And-Flip Method.
An alternate way that I am proposing (if anyone finds a reference elsewhere to this procedure I’d appreciate you letting me know) involves using a dial indicator and a miter gauge at your table saw.
See it here (easier than re-posting everything)
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