Considerations for making a 4-5 cm hole in a steel counter top?
You can use this type of bit. First drill a pilot hole of 3/5mm before using this.



Found over here

or this - but its more difficult - It says for wood but you can use them for soft steel as well but you need to constantly lubricate (lots!! dont be shy) the bit/surface to keep it cool using WD40 lubrication oil and drill at a slow speed. This is more dirtier and the edge can be rubbish.

Then you can mount something like this




These can be found at furniture shops/ swimming pool shops/ hardware stores.. you will need to find the one you need and possibly DIY it slightly.