Hole for new tap

[Vicario]

I decided to replace my old monobloc kitchen tap. My plumber removed it and then tried to fit the new (German) one. The hole in the sink top was too small! (31mm diameter out, 34mm needed). He did not have the tools necessary to enlarge the hole so re-fitted the old tap. He said that enlargement could be done by a kitchen fitter or maybe another plumber if I mentioned it when doing the booking, as some do have these tools. I can get another tap of the correct size, of course, but I've already got the new one - how would you proceed? The sink is made of that very hard white plasticky material and he pointed out that if done incorrectly there could be splitting of the unit (which cost about £400). (Why can't the required hole size be standard, as these taps are often replaced?)

 

[Rodders53]

Where did you buy the new tap from? Can you return and get a different one of the correct size (if such a beast exists nowadays, and you can determine the hole size needed from the suppliers/makers data - it's rarely mentioned).

Enlarging a hole in a granite / quartz / other hard material of any thickness is not a simple thing... and may even need access from both sides? A diamond grinding tool of some type to carefully and slowly enlarge (possibly wet / water cooled )... Search for < diamond finger milling bit > or similar.

Wait for advice from some of the professionals who know more than I...

35mm seems the most common hole size (taps being circa 34mm diameter), 28mm used to be used some time back... So your 31 is definitely an odd one out.