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I have been looking around for a box joint jig lately but decided to design one where I don’t have to set the blade width and opted for a adjustable advance mechanism to match the finger width to the slot cut by the cutter .
The object was to keep the build simple and made from common materials and components but not fixed to fixed index spacing like lead screw and index plate This is a simple sliding table with a fence that slides on a dovetail way and a clamping setup that is mounted on a sliding carriage that is controlled by two adjustable stops in travel length .
The parts to be machined are inserted and clamped by the bar clamp at the front of the jig and held square by the end stop which is typical for this type of jig .
The carriage is set for the beginning cut and held in position by the clamp located at the top rear of the jig .
To set the fence for the second cut I hold the fence with my left hand and release the clamp with my right hand and slide the clamping carriage to the opposite stop and lock it on the clamping rail and then slide the fence and clamping carriage over to the other stop and cut the second slot.
This same procedure is repeated until the fingers and slots are cut .
I remove the material from the jig but leave the fence locked in place for the next cutting sequence
To cut the opposing end I simply flip the boards end for end and start cutting the board using the setup in reverse direction .
So far the results are better then I expected and I will add a safety shield and a turret at the adjustable stops to accommodate different sizes of joint width .
This is a proto type and when complete it will likely include some improvements and changes in safety .
I used a stop block to limit the travel of the sled clamped to the saw to prevent the cutter from exiting through the safety block at the back of the jig but it does not show in the pictures or video .
Let me know what your opinion of this is and also any improvements that can be made I would appreciate it .
Here is a video link that may explain the jig a little better .

Wow Kiefer another great idea! Thanks for the video too, that really helped to understand how it works.The adjustable stops are genius.
If I understand, you start with the box sides next to the blade?
What would the turret add to this?

Thanks for the comment TIM
The start of the cutting will depend on the width of the box side so a layout would have to be done to fit the height of the box to have the joint centered and the turret idea is to allow a easy setup for different size cutters so I can switch without having to reset the stops .
This jig is a work in progress so any ideas for further improments are welcome .

Wow! This looks like a keeper. If you get the time to draw up some plans with measurements, we would all be interested. Very cool!


Thanks for your comment and interest Mike .
I am not one to ask for a plan or drawing ,I am just no good at it and when I build something like this I just start with the rough idea and build piece by piece .If anybody is interested in drawing a plan get in touch with me and I be willing to supply the information as required .
This is a proto type and I will likely make changes and additions as I see necessary .

Now I understand how it works. One of the simplest ideas I have seen so far for a box jig.
Well done Kiefer.

Tor and Odin are the greatest of gods.

Thanks for the comment and yes simple it is and easy to calibrate to get a exact fit .
I found that if it says 1/4" on a blade doesn’t mean that it will cut exactly 1/4" when in my table saw so I came up with the idea of being able to fine tune the advance on the jig to match the blade cutting width .
With a screw advance or fixed index like a threaded rod that can be difficult as the index from a 3/8" x16 tpi would give a 1/16" increment so I came up with this solution which kept it simple to build and adjust .

Another outstanding job of jig building.

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