Box Joints are one way of connecting corners in woodworking. They look great and when they are glued together they make a very strong joint which makes them suitable for drawers and boxes, especially ones that get high usage. The problem with most box joint jigs is that they are often finickity to use and very often will only make one, or at the most two sides at the same time. From what we have been able to gather, this jig was originally conceived by Lynn Sabin and later modified by others.
We have taken the original plans and modified them yet again, by primarily making the base much wider. The advantage to making the base wider is that the jig can now be adapted to cut wood flat side down. This means a type of weave pattern can now be cut into wood and not just on the edges.
Anyone who has tried to cut trivets manually on a table saw will be doing back flips when they see just how easy it is to make multiple cuts, accurately and easily.
Watch this Video on YouTube here - https://youtu.be/XEeWSepGqYI
We made the original version of this jig first of all to see how it worked and what problems we might encounter along the way. We were so happy with the first version that we decided to re-make the jig with a few modifications and changes to make it even better and more versatile. For more info and links, read on ...
The original plans called for the base to be quarter inch thick plywood. We opted to use a high quality half inch plywood because it was more rigid to work with and held the other jig components more firmly. The remainder of the jig called for three quarter inch plywood, which we did use, and we did select a very good grade for this because we wanted to end up with a quality jig that would last.
Another of the major modifications that we found in our first prototype version was that because the jig is essentially cut in half along the bottom, the whole jig tended to flex somewhat, which wasn't a problem except that we felt some of the joint may not have been as accurate as they could be. To help solve this problem the front sled part was made higher, which significantly improved the rigidity of the jig when it use.
The only other major component, aside from a few nuts and washers, was the threaded "ready rod". Depending on what blades you want to use the size of box joint sizes, you could select a variety of ready rod types. We selected a three eights by twenty, so that means 20 threads to the inch. What this gives us then in the jig, is for every eight turns of the ready rod, it moves the carriage by one quarter of an inch, which is perfect for what we wanted in making quarter inch box joints.
The plans that we used are kindly provided through the website www.sharkguard.com we appreciate that Lee Styron has provided this information ... and you might even find some products that Lee is making that will work with your equipment. The direct link to the slightly modified plans are here on the shark guard site
... <broken link> www.http://www.thesharkguard.com/lynnjig.php <broken link>
When cutting and assembling it is very important that all our components are true and that they fit together nicely. If you have the time and the material, we really suggest doing what we did and making up first version to see how it all comes together. Like anything, the second one is always better and in our case we found that during the construction of the first jig the back of the carriage, that is the part where the box joint wood is backed on to, was not absolutely at 90 degrees to the base. This meant that every box joint had a small gap in it and not a nice tight fit like was possible. When we found the problem we were able to partially fix it by gluing a veneer along the top to offset the angle. We made sure in the final version that we checked this angle as it is probably the most critical angle in the whole jig.
To lean more about box joint jigs see or other video on comparing box joint jigs as there is information on that video that will help you understand why we choose this version. Good luck and good building.
Joints Too Tight
It is not uncommon for these kinds of jigs to make accurate, and tight joints ... sometimes the joints are too tight, especially when it comes time to gluing which will also tend to swell the wood and make it even harder to get the joints to come together. This does depend on the wood you are using but all woods will swell to a degree when water based glue is applied. One thing that can help a lot is to run a metal file through each slot, one time. These files can be purchased new, or used many places and if you choose a coarse one that is 1/4" thick, it is perfect for easing the tightness of joints without compromising the a nice snug fit.
UPDATE: Lee Styron commented on our YouTube site about the t-Nut situation that many of you have asked about, here is his comment:
I do host those original plans on my site. I see a lot of questions asked below about aligning the two T-nuts so that they do not bind. Actually they will find their own position easily enough. Ideally you want them locked into place at the extremes just before binding. This eliminates any backlash and makes for solid travel. If the handle turns any, the carriage moves. No delay at all when turn the opposite direction.
Here is a link at Mcmaster to some nice T-nuts that are better than the standard cleat type.
Thanks Lee for this additional information, always great to hear from you!
It has come to my attention recently that Lee Styron, owner and producer of the Shark Guard blade guards, and the holder of the Lynn Sabin plans for this box joint jig, passed away on January 1, 2019. My sincerest condolences go out to his family. I only knew Lee from over the Internet but he was always helpful and forthright. Woodworking has lost a dedicated maker. For the time being, the Lynn Sabin Plans are still available on Lee's website on the links provided. At some time these may cease to exist but I have copies that I will post at that time.
MORE - It appears that the portion of Sharkguard website that contained the original Lynn Sabin plans for the box joint jig have been removed from the Internet.
I have managed to retain a copy of these orginal plans and since I have never been able to track down Lynn Sabin, and Lee Styron who kept those plans, has passed away, I now am making available through the plans section of this website, those orignal Lynn Sabin Plans ... in PDF formmat, and are free to download here - https://www.woodworkweb.com/free-woodworking-plans/func-startdown/743/
Copyright Colin Knecht