Size of Square to square guiderail?

[Lucky Dave]

Planning shopmade square to use to square guiderail for initial breakdown of sheet goods. Qwas square is 17", some use Woodpecker 18" or 26" squares, some seem to want to use 48". Setting aside for the moment use of square as a layout tool, just how large a square is needed for accurate (say less than 1/64" off at end of 4 ft cut) work? This question assumes you first create a clean reference edge.

 

[semenza]

    Personally I have found that using a square at least half the length of the rail helps  with setting it accurately. Depends how  long the short leg is too though.  I generally still mark from the square then set the rail (I know room for error). The trade off is not having to clamp or otherwise keep the square in place while setting the rail against it. It just works well for me that way. But I also extend the length of the square  by butting a 48" straight edge against it when marking.  I typically get 1/32" or less (most often less) over 48". Which makes less than a 1/128" error on the pieces that are then cut from that.  All other things being equal longer, fewer parts,  and fewer steps to the operation  is always better. That  helps remove human error which is why I would like a 48" - 50" square that has the tolerance of Woodpecker's.

Seth

 

[rljatl]

My 18" Woodpecker triangle seems to be perfect for that use.  YMMV.

 

[fshanno]

I'm no good at wide crosscutting.  When it comes to full sheet crosscutting the 1/64th you mention is as close as I ever get and I very rarely get that.  I'm tickled with 1/32 and will accept 1/16 with no questions asked.  Seems to always work out in the end.  Maybe it's cause I live an zany out of square world. 

Anyway, I use my Woodpecker 26", close my eyes and hope for the best.  Wait.  Maybe I shouldn't be closing my eyes?

Needless to say I always avoid wide crosscuts unless absolutely necessary.  The only time I make wide crosscuts is for refrigerator surrounds.  No choice there.  And even then I make the rip first.  I'd much rather make a 34" crosscut than a 48" crosscut.  I do pretty well on my MFT with the under 24" crosscuts.  Those are sometimes dead on and rarely more than 1/64th off.

On the other hand I'm very good at ripping and routinely get 1/64" accuracy on a full 8' rip.  In fact it's often dead on. 

Therefore I plan my nest to optimize for as many full 8' rips as possible.  I use eCabinets software for all casework and it has a setting that does a great job of maximizing long rips and minimizing long crosscuts.