My jig looks like the one in Mikes last photo, except my jig has a strip along the outside edge on top of what Mike shows in the last picture. These strips guide the base of the router to keep the bit centered, and when making the jig, you trim the edges of the slot using the router bit while the base of the router rides along each of these strips.
In use, the jig needs to always be used with the same router, router base, and bit, but it will cut a dado the exact width of the gap in the jig every time. So you can set the jig by putting the board to be inserted in the dado in the slot of the jig and move the two halves of the jig until it is tight against the board. Then lock the jig setting and remove the board. Place the jig on the board to receive the dado, position the jig where you want the dado and then clamp the jig into place. Set the bit depth and rout down along the left side of the jig and then back on the right side. The dado will be the exact width of the board used to set the gap width in the jig. No collars or bearings are needed. The router base and these upper rails of the jig do the guiding instead.
Central North Carolina
Last edited by CharleyL; 02-07-2018 at 08:53 PM.