I am installing quarter round over a new floating floor, against an existing baseboard.

Looked at much advice, pictures, etc on Internet (best was on HardwoodInstaller.com by Keith Soderholm), but cannot get satisfactory results. I am using what I believe to be an excellent and accurate table saw.
I set the blade at a 30 degree tilt and the guide at 90 degrees. I can cut a square piece of scrap lumber and get a perfectly mitered seam (i.e., the two pieces after cutting fit together like a glove).

But, when I do the same thing with the quarter round, I get a significant gap in the top of the quarter round. Any "expert" advice (and/or a demonstration!) would be greatly appreciated.

My spacial relations ability does not cover why my procedure works in square stock but not in quarter round.

Thanks. Ted

Could be the quarter round is moving once the blade cuts into it. It doesn't take much for it to happen. Are you cutting a hard hardwood with the quarter round and a soft hardwood with "the square stock?" A dull blade will do the same with hard species.

No chop saw around? You'll find there's more control cutting trim with it.

Yeah, a table saw doesn't work so well cutting long pieces of trim. Solve your problem by borrowing, renting or buying a powered miter saw.

Try cutting a small piece of quarter round and see if you get the same results. If a small piece of quarter round cuts correctly, then you need to look at the long length as being the contributing factor.

A power miter saw would work best, true, but you can have the same problems if you don't keep the boards from bowing.