Years ago when I was redoing my kitchen I tried making box joints with a shopmade jig and a wobble dado for some drawers, and after quite a bit of frustration trying to get it dialed in just as I wanted I eventually headed out and bought a half blind dovetail jig and knocked out the drawers in no time at all. Recently I was making a honey super for the beehive and decided that since box joints are the traditional joinery method for supers I’d give them another shot.
I did a bit more research and came up with some ideas for another shopmade jig, but in the process of doing so I also came across several glowing recommendations for the Incra iBox adjustable jig. I already had an Incra miter gage and found that it’s quality was sufficient to offset the sticker shock, so when I found that the tool budget was sufficiently stocked to acquire the iBox I ordered it.
The jig arrived well packaged and in good shape; for simply using cardboard Incra does an excellent job with their packaging design to minimize size and weight while maintaining protection from the bumps and bruises of transportation. I had already read the manual online and jumped directly into the very straightforward assembly, but before grabbing some test pieces I did take the time to at least glance through the provided instructional DVD. I did find the DVD to be helpful in terms of seeing the jig in action, and while I do not anticipate using the center key or splined box joint techniques it was interesting to see how these variations could be produced.
Once assembled and aligned to the saw, I found the jig very easy to work with. Initial calibration involves turning the adjustment knob until the jig’s “pin” touches the blade. After that, it’s a simple process of setting up your blade / dado and cutting height (note that this jig will work with standard 1/8” kerf blades if they have a flat grind, as well as specialized box joint blades and stacked dado blades; it will not work with thin kerf blades or wobble dados) then cutting a test piece. That piece is then used to dial in the associated pin width and offset. If the scap piece is the same thickness as the working stock, it can also be used to set the spacing for the vertical support / front blade guard. The most unique feature of this jig is that the offset is automatically set when setting the pin width, eliminating one of the primary weaknesses of most box joint jigs. Another simple but well designed feature is the use of an easy to adjust backer board to reduce joint tearout – loosen two screws, slide it over, retighten the screws and it’s ready to go. When the supplied backer board has been used up it can be flipped over and reused, and when a new one is needed the manual contains full dimensions for making a replacement (and the old one can also be used as a template).
With the jig setup and ready to use, cutting the joints is fairly easy. The combination of the front vertical support and the sturdy fence provides solid support even to tall workpieces, and the fence and rear blade guard combination is such that the natural and intuitive position of hands on the jig during use stay well clear of the blade. The guide bar is equipped with Incra’s slot adjustment system so that it ensures a smooth and wobble-free guidance from the saw’s miter slot. This makes the process one of setting the workpiece, making the cut, resetting the next piece, ….
The manual recommends using a clamp to secure the workpiece to the fence, but I have found that to be unnecessary except for the first cut of the second piece of a pair, when you index off the first cut on the first piece and when that piece is removed there is not a sold index remaining. It is possibly also helpful if cutting relatively narrow workpieces to ensure they stay level during the cut as, by necessity for this type of adjustable jig, the area between the blade and the pin does not have any workpiece support.
After cutting the first joint (depending on the project you may want to use scrap for this first set), check the fit and if it isn’t quite right the jig can be dialed in with 0.001” resolution until the joint falls together. This is where the this jig beats anything else on the market or shop-made, and it’s the first jig I’ve ever used where I have to make sure to remember to account for some glue space in the finished joint.
All in all I’m very happy with this jig and the results I have obtained using it – and I may well start using box joints far more often given the ease of making them delivered by this jig. Can a simple shopbuilt jig get the same results? Sure – if you’re incredibly lucky in making it. But can it adjust to different pin widths and depths in a matter of seconds, or be used to tweak the fit of an already cut pin? That flexibility is where this jig excels.
Relative to the statement made earlier about the jig not working with certain blades, the thin kerf limitation is due to the width of the jig’s alignment pins being just a hair shy of 1/8 inch, so physically a smaller cut simply won’t fit over them. The wobble dado limitation is, as far as I can tell, not a true limitation but an end product quality recommendation and a headache reduction suggestion. If you were to somehow find yourself needing to make box joints with this jig and a wobble dado, my belief is that the basics of the jig could (with quite a bit of guesswork and effort) be made to do the job as a fancier version of a shop-made non-adjustable jig, but the adjustment feature would be essentially useless due to a stacked dado referencing from the arbor flange whereas a wobble dado references from the center of the dado blade. If you are considering buying this jig and you only have a wobble dado, please do everyone and most of all yourself a favor and get a stacked dado.