For any material and almost any size hole, I often will make a test hole in
a scrap piece of plywood or 2x4 and test fit my piece before making my mind
up about the proper size.

One thing to consider is that the thermal expansion coeficcient (how much it
expands when it gets hot) is probably different for the metal of the faucet
and corian. Any extra hole space may be needed to allow for expansion of
the materials without binding or worse yet, cracking. I doubt the
difference needs more than 1 or 2 tenths of an inch of extra space to
prevent a problem though. Extra hole space also allows for removal if the
pipes become corroded or caked with old plumbers putty.





"toller" wrote in message
...
I have a single hole faucet in my Corian sink. It is pretty beat up after
only 6 years and I am replacing it with a 3 hole faucet. I have to cut 2
new holes.

The installation instructions call for 1 3/8" - 1 1/2" holes, but the
posts
only measure 7/8". Wouldn't I be better off using a smaller hole? 7/8"
might be pressing my luck, but I have 1", 1 1/8", and 1 1/4" hole saws
(but
no 1 3/8"?!)

I presume the extra size is to allow for incorrect placement, but I ought
to
be able to get them within an eight of an inch. Or is there another
reason
I am missing?

I don't have a whole lot of experience with hole saws, but I would imagine
that I can start to cut 1" holes and then confirm that the faucet fits
before cutting through. If it does not fit, then is shouldn't be too late
to go to a larger size, should it. (obviously once the hole is finished
there is no way to fix it...)

Thank.