Undermount sink cutting on oak wooden worktop 40mm

[Mr Chibs]

Currently fitting my new kitchen.

As I like making things difficult for myself, I've decided to have an undermount sink and was wondering if anyone has any tips before I start. Have a 40mm oak worktop.

I had intended to use a router with a top bearing bit and make up an mdf template.
What's the proper method for the first few cuts, as the cutter has be be fully into the worktop for the bearing to track along the mdf template.

I have seen a post mention 'guide bush' for the router, which I can buy, but I've never used before.

TIA

 

[Lower]

If you use a guide bush, the router itself is guided throughout the cut and isn't related to the depth of cut.

I wouldn't try and use a bearing guided cutter.