4" Pvc Pipe, 3" Netcups, What Size Hole Saw?

[MediMary]

Hi, I am setting up a system using 4" pvc pipe and 3" net cups.
I have a 2 7/8" (73MM) hole saw, on a flat surface it works perfect(cuts nice flush hole) but on the convex surface of the pvc pipe it makes a hole that is too large and the net cup wobbles around.

More than likely will have to order online as the local hardware store doesn't have much of a selection. I wrapped tape around the net cup to try and gauge the correct size, but if anyone knows the exact size it would be greatly appreciated, or if you know a thread the info might be in, I'll be happy to search it if you can post a link.

 

[Jack og]

Hi, I am setting up a system using 4" pvc pipe and 3" net cups.
I have a 2 7/8" (73MM) hole saw, on a flat surface it works perfect(cuts nice flush hole) but on the convex surface of the pvc pipe it makes a hole that is too large and the net cup wobbles around.

More than likely will have to order online as the local hardware store doesn't have much of a selection. I wrapped tape around the net cup to try and gauge the correct size, but if anyone knows the exact size it would be greatly appreciated, or if you know a thread the info might be in, I'll be happy to search it if you can post a link.

2-3/4 “ works better but on a convex surface it still needs a gasket