Fitting a surface mount basin

[PilotPete]

If you fit a surface mount basin to a worktop, should the worktop have a hole cut the size of the waste (40mm) and then the waste 'nut' tightened up to the bottom of the worktop, or should the worktop have a larger hole cut in it so that the waste 'nut' tightens up to the underside of the basin?

It is a Villeroy & Boch 'Loop' basin without overflow waste (if that makes a difference).

Cheers

PP

 

[Newboy]

backnut should be tightened up to the basin - otherwise the worktop will be forming part of the seal & the waste will be supporting the basin