Box Joint Modification

[Bill Adamsen]

When using box joints on drawers, running the sides through to cut the bottom slots leaves the slot showing on two of the four sides of the completed box. This is easy to "plug" after build, but I got thinking why couldn't the joint be like a half-blind dovetail and hide the slot? So just fiddling around, I did the equivalent with the box joint and it worked fine with minimal additional effort. Not as strong but easier to apply the glue. For something using these "low end" joints, I'll probably stick to the normal approach. Thought I'd share.

[John TenEyck]

That's pretty cool, Bill. Makes perfect sense but I've never seen it before. I'm sure it's still plenty strong. There is so much glue area in finger joints compared to most other 90° box joints that it won't matter.

John

[Mike Manning]

So how did you do the half blind box joints at the bottom? Unlike John it isn't intuitive to me. :-)

[Bill Adamsen]

Just rabbeted the end to the same depth as the bottom dado, and removed that same amount off the tongues on the mating piece.

[Mike Ontko]

Nice and clean, Bill! I recently went through the exercise of building a jig and making my first box joints but didn't consider the gap left by the bottom groove. It's not much of an issue when used in drawer construction because the drawer front panel covers things up. But pretty much any other box joint application requires something--like the plug you'd mentioned or the alternative method you've discovered.

[Steve Lansing]

I like it! I'm sure I'll try it some day.
And I agree with John - "it's still plenty strong"

[Bill Adamsen]

Looking at the drawing now I realize a further modified joint - with the rabbet on both pieces - would provide even greater advantage. A cleaner look still would have a mitre where the sides meet. With the standard joint one has to be careful to get the bottom slot exactly on the tongue. With a dual rabbet modified joint it wouldn't matter where the slot was cut, because it wouldn't be seen after assembly.

Doing this has gotten me sidetracked enough to look at some other possible alternatives. One with promise has one side having a full mitre so that no "joint" shows up from a side profile. Another has the same look as the "mitre" version but in fact is cut on the sled laying down at 45° so the the entire joint is a locked mitre. I built the sled to do that last night, but want to see if I can actually cut a joint feasibly using it. In some ways, it would simplify the dimensioning of the joint.

[added the second "advanced mitre" image]

Speaking of rabbet ... "Rabbit Rabbit"

[Stan Calow]

Bill, I am inferring that you need to have sides that are thick enough to allow for the shorter fingers. I've been using routed stopped grooves in the sides to avoid the gap, but like your idea better.

[Bill Adamsen]

Stan ... I think (though I haven't tested this) that the scale should work irrespective of the thickness. Though there are practical limits. Again, it is primarily a solution for when the sides of a box made with a box (finger) joint are going to get a groove for a bottom or lid such as in a drawer box. To your point, a stop works great, but on a router table not on a tablesaw. I happen to cut mine on a tablesaw with a sled. I also suspect it is easier to cut the groove without the need to think about stops no matter where the slots are cut.

Back to the thickness question ... for drawers, I typically use bottom-mount slides (Blumotion 683H/569A/etc.) and the math for the width registers off the inside of the drawer box. So I try to keep the math simple with drawer sides of 7/16", 1/2" or 5/8". Then the bottom panel slot is about 1/3rd (or so) of the side thickness. Any of those thicknesses should work fine I would think. Again, this was just an exercise to see if it worked.

[Alan Schwabacher]

Or you could simply glue on drawer slips to hold the bottom.

[glenn bradley]

I use a slot cutting router bit and cut the slot around the inside perimeter at the router table with the box dry fit and clamped. To each their own.

[Rick Moyer]

I use a slot cutting router bit and cut the slot around the inside perimeter at the router table with the box dry fit and clamped. To each their own.
Yep, started doing this as well. You can create whatever complicated joint you wish but for regular box joints a slot cutting bit make a nice fitting hidden dado bottom.

[Bill Adamsen]

I can see the slot cutter being preferred if the box joint is a different size or location than the bottom. I happen to typically use a 1/4" bottom and same size box joint cutter, so I just run the sides through the same dado for the bottom slot. It is very quick and easy and doesn't require setting up a different machine or pre-assembling the box. Just set the fence to align with a tongue. Then I plug the hole with a cutoff tongue. I need to plane and sand off the tenons post gluing anyway, so it doesn't really add an extra step. And visibility is low. As I indicated in the original post ... likely the way I'll continue doing it with softwoods. For hardwoods I'll stick with the dovetail.