Having just browsed Pat Warner's website, I stumbled across his mortise/tenon jigs.

Since I'll have to equip my not-ready-yet shop, I was thinking about buying a Festool MFT and use my Festool OF1400 router for this (instead of the jigs Pat Warner uses).

However - no matter how I were to do it - there's something I can't figure out:

How do you make sure that the mortise and tenon have the same width/thickness - i.e a tight fit ?

Looking at Pat Warner's website - you control the width of the mortise either by the width of the cutter doing only 1 pass - or by doing more than 1 pass.
The width of the tenon is controlled by the cutter itself.
So - how do you make these two fit precisely ?

I could imagine that if the stock used for the tenon was just 0.5mm thinner than what you had planned - then you'd end up with a loose joint.
Also if doing more than 1 pass for the mortise - I could imagine that everything would have to be VERY precise (guides, etc.) in order to get a tight fit.

All of this is based on me not having much experience with a router (yet), so forgive me if this is basic knowledge

What am I missing here ??

Thanks,
Niels