I can cut at least 1,6mm FR-4 with an ROLLER BLADE CUTTER,like this one bellow:
The only true problem for me is : i don't know the brand and model of this kind of manual tool to get.
Maybe me alone will find something on amazon.de.
There are $300.00 "PCB cutting" machines with large, >4" circular blades that passively roll. If I understand correctly, even they cannot cut PCB; they are actually designed to separate PCBs that are already V scored. Or maybe I'm wrong.
If you want the bees knees, carbide is the way to go. Manual scoring. Or power/rotary cutting action. Think router table but with a smaller carbide bit.
My Dremel tool router table cuts or V scores PCB like butter. Shapes, too. Circular PCB's, curves, slots, anything I need. Cutouts in housings. Making custom bushings. Machining Delrin or HPDE or wood. And it cost me about $100.00 for the table and the Proxxon rotary tool. Of course it also took a bandsaw and about 12 hours to make it.
The key is that it has to be able to tilt to 45 degrees so an endmill can cut a V-groove in the PCB. Otherwise the kerf would be too big. There are pointy carbide V-cutters, the kind some people use for machining PCB traces in the coper layer. But they wear out almost instantly in FR-4, and the chatter is terrible.