MFS size for hole Dia template

[ActivePro]

Hello All

I want to make a hole template using my MFS jig.
I have a 30mm router guide bush with a 10mm router bit.
The circle inside hole size needs to be able to cut 80mm circles.

So to cut a circle I think I would need to set my MFS at 40mm - 5mm for my router bit and this would give me my inside 80mm circle but I also need to insure that this hole size is big enough to use as my temple to cut 80mm outside circles so it has to be bigger.

Would it be 40mm - 5 plus 30mm for the bush — 75mm to cut the inside circle template
Can anyone help on this please I am getting confused just write this to try to explain lol

 

[Coen]

You want template (hole) that you are going to copy from the inside using 30 ring, 10 bit to get as an end result a hole that is 80?

Then the template hole needs to be (80+30-10)=100

I would just grab the holesaw 80mm