Started on a workbench build recently. Dimensioning 12/4 poplar for the base. Face joint - thickness - edge joint - rip. Pretty standard. I squared my jointer fence to the bed using my 12” Starrett combo square. Similarly, I squared the table saw blade to the table using the Starrett. When all was said and done, I found that I had two 90 degree edges and two edges that were slightly out of square. These pieces are 2 3/4” by 3” and 4” for reference. After thinking it over, and checking all my setups agains, I came to this conclusion - when having to rip thick stock, I typically rip it on my bandsaw, 1/16 or 1/32 oversize, then clean up the edge on the table saw. I know this seems like extra work, and it is, but I hate pushing thick stock over my 2hp table saw and hearing it bog down and struggle. My bandsaw equipped with a 3tpi resaw blade goes right through 3” stock with ease. So I concluded that ripping 1/32” or 1/16” off the edge of a board is causing my table saw blade to deflect away from the workpiece, considering there’s nothing on the other side of the blade to counteract the deflection. To test this, I ripped my workpieces thinner, just by a few thousandths. This time, in an attempt to reduce the amount of deflection, I pushed the stock through very very slowly - ending up with some burn marks - but alas - the piece came closer into being perfectly square. Using my Starrett and feeler gauges, I found that some pieces are out of square by 0.002” over 3”-4”. I’m satisfied with that. I wish it was perfect, but it may just be the limitations of my machines. I often have to remind myself to not become obsessive over chasing “square”.

Bottom line. 0.002” over 3”. Is that square enough for you?