The router attachment simply consists of a motor in a cylindrical mount that attaches to the Z axis like the others. The motor can be of different sizes depending on what materials the user is working with. The motor has a collet type chuck and holds the bit securely while in sideload.
I have been using bits smaller than 2mm for most of my projects as they leave a nice smooth edge on woods and a super smooth edge in plastics. Here is a general look at the motor attachment:
This motor is about 2 inches around and 2 1/2 inches long with ball bearings on both ends I made several of these motor attachments including one with a very large shaft for use with a drill chuck. I must confess I never used it as a cnc driven head however it is handy to use a drill press by steering the X,Y axis with the joystick and then drilling with the Z. I have never had the need yet for drilling so many holes in a workpiece to set up a program for doing that.
I do use this to make a prototype PCB from time to time and the holes I drop in the router bit. Normally I mill pcbs on this with a .5mm to 1mm bit so it works out ok but does add wear to the bits. I have been buying these bits at a pretty good price though so I don't feel to bad about it. I also have been using more phenolic PCB material instead of FR4 and that also seems to help if I dig a little deep on the traces(sloppy setup on my part).
The nice thing about the smaller motor9if you can use it) is less noise and screaming from the machine running a part. I often use this machine in my house so noise can be an issue sometimes(cats hate it) But I have more horsepower available if I need it and the attachment swap fast and easy.