LeeWay Workshop -Box Joint Jig

LeeWay Workshop

July 25, 2008

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Lynn's Jig. More stable design. Dimension's included. Photo INTENSIVE!

Lynn Sabin's Basic Box Joint Jig
This is a great jig for doing Box joints in your projects. Mad Marks site is no longer available so I hope that he doesn't mind that I am taking the liberty to post his instructions for this jig on my site. Mark, if you mind, let me know. Thank you for the plans for such an accurate and easy jig. Here is the link for the instructions in PDF Format.

Lynn certainly designed a quality jig here. It can be adapted and built a lot of different ways. I have since built the jig bigger and on a sled and that link is at the top of this page. The "Lynn's Jig" is very precise and easy to use. I have added a few features that improve the jig in my opinion. Some are subtle changes. Some are more obvious. All of the wood parts are 3/4" plywood. I originally built the 24" version from the plans at Mark's site. The plans here are for a 30" version. The larger the jig, the wider the boards that you can put box joints on.

This jig will do box joints on stock 13" wide. If you would like to make bigger ones, you only need to extend the length of the carriage, back, and threaded rod. For example, you want to have a 16" box joint capability, make the carriage 16" and the back 35". The threaded rod would then be about 42" or so.

This is the hardware needed to build this jig. You will need:

3/8" 16 Acorn nuts - 2
3/8" 16 Hex nuts - 6
3/8" 16 x 36" Threaded rod
3/8" 16 Tee nuts - 3
3/8" Washers - 3

I used 1/4" carriage bolt, nuts, washers and a golf ball for the knob. You can use any kind of knob that you wish. Smaller than a bowling ball is suggested.

This part is a brace that gets screwed on the back of the carriage. This will help if your threaded rod isn't exactly straight. It will keep the carrige in line with the back of the jig.

The handle is a bit different than Lynn's. Again this was just my choice. I felt that a handle was better than a knob because it was just easier to keep track of the turns.

I made the two ends( B and G ) 3/4" longer to give the jig a little more footing. The extra 3/4" sticks out behind the jig.

I made parts C and E identical beause I added a clamp to the front side of the carriage for holding the stock. The screws in the carriage should be at least an inch up from the bottom of the jig because your blade will be cutting through the bottom of the carriage.

D is the back of the carriage.

F is the back of the jig.

H is the 3/8" -16 threaded rod

This carriage clamp holds the stock firmly in place in the carriage and allows the stock to move with the carriage freely. The diagram shows locations for 4 bolts. Two bolts is sufficient to hold the stock in place. The main reason the I use this clamp is that I always cut the 4 sides of the box at once. Then I flip end for end and flip again to make the second set of cuts. This lets yu cut the joints for the entire box with just 2 passes on the Lynn's Jig. Below is the lock nut detail that is used on the handle side of the jig. You don't actually tighten the nuts on the side, but just snug fit and jamb the second nut on each side against the first to keep them from moving. This effectively holds the threaded rod in position while turning and allows the carriage to move back and forth on the rod when it is being turned.