Hole size for a faucet in Corian?

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.
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I had a solid surface bathroom vanity top that didn't have holes either. I got a mansonry drill bit. Wasn't corian, but by transolid.
You should be able to drill smaller holes but you must make sure it is even. The oversided holes makes sure the faucet isn't crooked. Also, don't force in the supply lines from the faucet, they will kink.
My biggest problem was starting the hole. The drill bit would move off the mark before it made an indent. I recommend having a shop vac going because it make quite a mess.
c_kubie
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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.

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