Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4321742.
This gives precision lift capability to a standard plunge router enabling it to be mounted under a table.
The hardware used will be very much dependant on the router model and table used. As an example, my silver line router had some convenient points in the aluminium base to drill some holes and, using a few washers, anchors the threaded rods nicely. your mileage may vary. The only 3D printed part that needs specific hardware is the metric 8mm quad-start 2mm pitch lead screw. This is the same as used by most 3D printers Z axis lead screws so should be readily and cheaply available. (I would suggest getting a 500mm instead of the 300mm I bought as this would reach all the way up to the router base and not need the 3mm threaded rod coupled on to it like mine. I will be replacing mine at some point.)
The basic premise is one side of the arm is 'stationary' and another is designed to move up and down on a turning lead screw. The lead screw needs to be mounted at the router base end to allow rotation but also to allow pivoting (as the arm arc will cause the bottom end of the lead screw to move in and out). I used a convex washer for this. Also, to mount the threaded rod to the rocker arm, the included axles should be glued in once in place in the rocker arm. I used plastic weld to provide a very strong bond. But be careful it doesn't get onto the rocker arm as this would stop it from pivoting correctly.
So hardware goes as follows, top to bottom:
3mm threaded rod locking nut washer convex washer router base (through drilled hole)
big ole gap
8mm bolt running laterally between rocker arm holes with 4mm hole drilled perpendicular, through which the threaded rod can pass washer locknut
Rotating side: 3mm threaded rod double locknut (this is where the socket goes to wind the router up or down) washer convex washer router base
big ole gap
coupler to 8mm lead screw (with zip ties to stop it spreading under load. Really, really needs reworking as this is a total bodge)
8mm lead screw threaded onto the threaded 3d printed part