Reply by Manitario

I’m not too sure what the limit of error in a square that is detectable by the human eye, but I know that an error of 0.5 degrees results in a gap on my mitres or a gap between the rail and stile on a raised panel frame. On my jointer, if the fence is not set to 90o the edge joints don’t come together perfectly. I have a number of squares, some cheap, some not. Finding a perfectly 90o square from a big box store is hit and miss, or having said cheap square stay 90o is also hit and miss. When I pay more for eg. Starrett, it is because I know that it will be 90o out of the box and will likely stay 90o for many, many years.

-- Rob, Sault Ste. Marie, Ontario