Hi Cliff,
I own a Grizzly 9x20 and it will accomodate tools up to 1/2". However, I rarely use such a large toolbit. I use mostly 1/4" - 3/8" toolbits, smaller ones for closer work, larger ones for taking off more material. I'm becoming a great fan of the indexable tooling and I use that in the 3/8" size.
Cheers,
Phil