u/MikeAnblips

Hi, In woodworking parlance, you'll hear "dead flat" and "dead square", but also "flattish" and "as flat/square as I could get it".

As an anxious novice, I don't know too well what to do with those qualitative statements, and although I'm pretty sure that there is a "code" for achieving the precision needed for the task, I'm struggling to crack it.

Probably if you use a planer/thicknesser you don't even bother, leaving it to the machine to determine your precision, however if you happen to prep by hand, would you mind sharing your criteria for "flat" and "square"?

Right now I tend to "cup" in both dimensions (so a slight hollow length and width wise), measured with a straight edge and feeler gauges. I'm happy if I am under 0.1mm, or 0.004". This, for the pieces I've worked with so far, max length probably 60 cm (24"), width 30 cm (12").

I don't mind fettling, however I'd like to do it where it's needed and it makes sense...

Thanks for sharing your wisdom 😇