Squaring wood sheet that’s un square on all sides

[cmoops2]

SPECTRIC makes a very good point when he says: "If the edges are OK ..."

Unless I specifically need every square inch of an 8 x 4 (2440 x 1220), I deliberately seek out sheets with less than perfect edges and then negotiate a good discount (if you don't ask you don't get !). That said, I do remain fussy about the quality of the face veneers. It's then time to get going with the track saw guide rail to produce one good reference long edge (from which all subsequent rips are made). As mentioned by many others, I then establish the first cross-cut reference edge using a bit of good old-fashioned 3, 4, 5 (or 5, 12, 13) or a big framing square before proceeding with all the cross-cuts ...

 

[throbscottle]

Though it is still reliant upon the accuracy with which the geometry is transferred to the material; the straightness of an edge, the thickness of a pencil line…

Not to mention the skill of the geometer...

 

[cowtown_eric]

Alhough I've frequently encountered "out of square" on 5x5 baltic birch,it is not really common (but I always check!)

First thing I would do is check my square.... you'd be suprised at how many rafter squares are just a tad off-particularly used ones!