Grinding Stainless Steel

[gumboot]

I need to enlarge a 55mm diameter hole in a stainless steel kitchen sink to 90mm in order to fit a waste disposal unit called an "insinkerator" to the sink.

It looks like I'll have to grind the stainless steel away around the plug hole until I reach the required diameter for the waste disposal unit assembly.

I'd like to know if anyone has any tips or advice they could give on this matter. What I'm concerned about is the likely hardness of the stainless steel. Whilst I know that the metal is relatively thin and should be able to be ground out with a grinding wheel, I don't know how hard the stainless steel is likely to be. Time is really not an issue but can the job be done with a small grinding wheel in the chuck of a mains powered electric drill? Unless, I'm very much mistaken, this type of job is beyond the scope of grinding wheels in Dremel type tools.

The position of the sink precludes changing it for a new one with a 90mm hole already in it - removing it would damage an expensive worktop.

Thanks in advance for all replies.

[wildwood]

I can see of sorts of accidents if you try to grind it with a grindstone/drill.

Why not go to a plumbing store/workshop and see if you can buy/borrow a proper utility to make the hole bigger. It basically looks like a bolt&nut with very two thick wavy washers. The specially shaped washers cut into the steel as you tighten the nut and cuts a neat hole in the S/S.

[heathfield]

The present waste fitting will be in a dimple in the bottom of the sink, which will allow all the water to fully drain out. Some sinks come with a large enough dimple that will take a 90mm cut-out, but if not, it's likely that the waste disposal fitting will sit proud of the base of the sink, and you'll always be left with some water that can't drain away. Not a happy situation!.

But there are commercial tools that get around this by 1) cutting the new hole, then, 2) producing a new dimple. There's an example showing the process here.

You might have a problem finding anyone locally who has this equipment - I can't see it being commonly available. Good Luck!