I have no experience with corner sinks but am planning a 32 inch 1 3/4 sink in my kitchen. Just to be sure the sink would fit, I did not trust my designer, who has measured everthing wrong so far( they are ordering 3/4 of the new cabinets at their expense). I have had Lowes and 3 other firms help me with this. I have been told that a 33 inch sink will fit undermount in a 42 inch cabinet if the sides are scooped. A 30 inch fits without scooped sides. This has been a consistent thought by all 4 kitchen people. Hopefully someone with a corner sink in a 42 inch cabinet will verify. G

A 33" sink will fit in a standard 36" sink base, not a corner sink base. We have a 15-3/4" x 15-3/4" sink in a 36" corner sink base. We might have been able to go a little bigger, but definitely not a 33" sink! The front of a 36" corner sink base, btw, is only about 17".

Our corner sink:

Imagine a sink more than twice its size and you'll see that it wouldn't fit.

Here's what it looked like before countertop.

We are almost done with the process of installing our cabinets ourselves--due to a change in circumstances this has turned into a DIY project from a professional installation. We have a 42 inch corner sink base--the 42" is measured from one of the cabinet sides adjacent to the door to the opposite cabinet side. If ours was the unit the last picture above the cabinet side just to the right of the door would be 42 inches from the cabinet side that is attached to the kitchen's wall. For our setup, we can go up to 33 inches for an undermount, bigger if we put filler pieces between the sink base and adjacent cabinets or if there are no top drawers in the adjacent cabinets. If you want to go with the 33 inch sink, you need the 42" corner sink base.

Hope this helps. We're still trying to pick out our sink--we only have to install the sink base and a couple of relatively easy other cabinets in this week so we can get templated (no pressure).

Good luck!