I have both a 6" and an 8" dado. Both work just fine. The only advantage I see to a larger size would be depth of cut which would be seldom if ever needed.
If you ever decide to get the Incra Ibox, it uses up 1/2" of your depth of cut, so the extra 1" depth of cut provided by the 8" dado may come in handy if you do deep joints.
I've used a Forrest Dado king 8" for years on my shopsmith. Never had a problem.
Matter a fact I just used it to make shelving at my son's new house, with my old .75 hp Dewalt MBF RAS. I had to feed a little slower, but worked fine.
I do use it with the I Box Mike. Never thought of that. So far, I've never needed more than a 3/4X3/4 cut, though.
I also use Freud SBOX8 Box Joint Cutter Set, which is 8", with no problems, either.
Mike907 wrote:If you ever decide to get the Incra Ibox, it uses up 1/2" of your depth of cut, so the extra 1" depth of cut provided by the 8" dado may come in handy if you do deep joints.
Mike
Gene
'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton