The stainless steel sinks may have two types of holes, which are drilled for the usage of the accessories such as waste fitting and faucet. So normally I would like to mention them as the outlet hole for waste and faucet holes.
Although the overall holes on the stainless steel sinks are only two types, I often get problems in these “hole” issues. The difficulties come from the communication obstacle ( me and the client speak not good English) and their rich sizes. The diameters of outlet holes has 55mm, 70mm, 110mm, 114mm, 140mm, 160mm etc. About the diameter of outlet holes, please check this picture first:
let us take the 110mm waste hole as an example, the outer diameter(red part to rest the disk of the waste fitting) is 110mm, but the inner diameter is 89mm (the black part, I also call it see-through part). The 89mm diameter is same as the 3.5″ hole that we talk all the time. You can see now where the ambiguity is. It is hard to clariy wheather the clients is talking about the outer hole or inner hole diameter.
And another most often required size of the waste outlet hole is 1.5″, but actually the 1.5″ is not the size of the waste fitting, it is the size of the pipe like the picture. Yes, 1.5″ is the standard diameter of the pipe underneath the waste fitting. I haven’t heard any other sizes for the pipe diameter other than 1.5″.
The faucet hole is easy to tell. The most often used diameters are 28mm, 32mm, 35mm, 38mm. Just let us know about the size of the faucet hole and the distance between it, then we can make exactly for you.
In summary, the holes on the stainless steel sinks may be done wrongly if we confuse with the sizes that we are talking about. We need to be careful for it.