Haven't done much dado'ing on my tablesaw, usually clamp up a straight edge and use a router. But I just set up a 2nd saw in my shop to be dedicated for a dado saw. So I haven't built any cross sleds yet for it which are certainly around (lots of plans). Especially complete with the concept of replacing the bottom with 1/4" hardboard pieces to create 0 clearance for the basic sizes I'll be using.
So without having one, here's what happened the other day.
A pal comes over & says he wants to build a bookcase for his Church as a donation and arrives with a couple sheets of 3/4 oak ply (4x8 size). He asks me what depth the shelves should be. I suggest a foot or so. He says he'd like to have them at least 16" deep.
So using the concept of cutting the dado right across the piece of 32" plywood then ripping the side in half to enable perfectly lined up heights, we go about it. He wants the bookcase 76" high as well. After setting the dado and the fence I'm looking at this 32" wide 76" long slab of plywood and wondering how I'll keep it against the fence to make a clean - non wavy = butchered cut. The 1st one goes okay but it was close. I saw a small gap appear against the fence appear at least 2x. As I got to the other dados, (he wanted a bunch of shelves), the difficulty in keeping the end against the fence didn't improve. At one point my friend thought he'd help and pushed the panel which of course immediately butchered the dado and had me visioning a 30lb chunk of plywood coming off the table at me. (but it didn't) whew.
The 32" width negated me using my miter guage to start the cuts as the panel was over the edge of the table to engage it.
I think this is one of those cases where a dedicated dado sled would have been the answer, (if it was wide enough) My question is do any of you cut dado's on wide panels on the tablesaw and if so, how large have you made your sled & to what level of success? Or ... is this just a "not to do again" and on wide panels to use the straight edge & router method?