Here is a Slot Mortising Machine I made mostly from bits and pieces that I had lying about the shop. It is therefore, by far the cheapest machine I have and a very handy addition to my workshop.
I use it for cutting the mortises for floating tenon joints, spline mitre joints and for any slotting work that is required. The machine comprises X and Y tables that run on drawer slides and a router that is mounted in a height-adjustable plate so that I have Z adjustment as well.
There are stops for delimiting the cut distance and a depth stop for controlling depth of cut. Clamps hold the work down and a mirror enables the blind side of the work to be seen.
The mechanism in front of the tables controls the depth of pass (1 turn of the black knob = 1/32″) so there is no stress on the machine or on the work. The machine is a real pleasure to use and is always a talking point when visitors enter my workshop.