Attachment 20232To get started with an adjustable Box joint Jig, I bought a pals to adjust the saw blade parallel to the rails within +-.003 The plan was from American Woodworker #133 January 2008
The runners were made from Hard Maple. They were shimmed to the out side of the slots, with very little clearance.The base and fixed fence are glued at 90° Put a weight on the base and let it dry.Then you can go ahead install screws later.
Attachment 20234The small section is fasten to the fixed fenced fence.The adusting is with a 1/4-20 x 6" eyescrew bushed both ends. It really adjusts,very nicely.
Attachment 20237The adusting fench has two 1/4 x 20 thumbscrews
Attachment 20235I added 4" to the back for extra weighThere are several things that were different from the original that I went ahead change the plan. It has been a very hard working Fixture.Very nice to use.