Box Joints

[Jerry Lawrence]

I have been asked to make five identical boxes out of 3/8" birch plywood, 5''x6''x10'', with box joint corners. After cutting the pieces to size, can I clamp the same size pieces together and run them over the dado blade all together to make the box joint 'fingers' in all the pieces at once, or is there a problem with doing this? Never made box joints before, so plan on doing test pieces with scrap, and making a jig to keep the spacing even. Any suggestions or problems to watch for would be greatly appreciated.
Thanks!

[Charles Lent]

Once you have the jig and dado blade correct and have made one box successfully, yes you can clamp groups of similar sides together and cut them. But make certain that you have the jig set up correctly or you will make a lot of scrap. When I do this I also label each piece, A for the front and back. B for the sides. The position of the pins has to be offset on the B pieces. You can also cut all pieces at once if you can come up with a way to offset the position of the B pieces by the exact width of the pin and slot. I've stopped using my dado blade for box joints. I bought a Freud box joint blade and am very pleased with the results. It makes perfect splinter free 1/4" and 3/8" box joints.

Charley

[Jerry Lawrence]

Two follow up questions: One, would it be easier to do this using a dovetail jig with a straight bit? (and no, they specifically want straight fingers, not dovetails). And two, sounds like a stupid question, but once I get the joints cut, is there any good way to minimize the amount of glue mess left from gluing all those fingers together? The tops and bottoms of these boxes will be just more plywood glued to the outside of the frames. I was going to try gluing the whole thing (corners, top and bottom) all in one operation, but am now thinking maybe I should just glue the frames first to make it easier to clean them up inside and out before gluing the tops and bottoms on. Sorry if it seems like I'm overthinking something that someone else could whip out in their sleep, but I've never done this kind of corner before and I just want to make sure these come out right.
Thanks again!

[Myk Rian]

You have to offset the 2 sides or ends 3/8" for it to fit together. If you cut them all the same, then you will have to trim 3/8" off the ends, and the sides.
Hope I said that so it is understood.

When I make box joint boxes, I use a brush to put the glue in the fingers. There will always be some squeeze-out.
For the bottom, I make a dado in the sides and ends to fit the bottom in. That's the sturdiest way to do it.

I use an Incra jig to make the cuts. Very accurate to the point of them almost being too tight.
Try your setup and technique on a scrap box first. It'll save you frustration when making the real thing.

[fRED mCnEILL]

If your jig will accept multiples, no problem doing it. My jig will accept 15 one half inch pieces of Baltic birch at one time.Great time saver. Li can do 1/2 dozen drawes at one time.Just make sure you use a sacrificial piece so their is no tear out on the last piece.

[Alan Schaffter]

Since it sounds like you are a real newby to box joints, spend some time learning about joints and box joint jigs (retail or DIY). Setup is critical- the blade setting, index pin width, and the space between the index pin the blade must all be adjusted so they are the same size with an accuracy of a few thousandths of an inch! A well made will allow you to cut multiple boards at once, but secure clamping is essential so they stay perfectly aligned, at least for the first cutting pass.

Also, look at other boxes made with box joints to see how they are made. Rather than cut each board with an A and a B end, I think it looks much better to put two A ends on sides 1 & 3 and two B ends on sides 2 & 4 even if you are not using contrasting colored wood.

Does the customer want the dimensions to be exactly as you stated, or do you have some leeway. Do you want full-width first and last fingers on each joint? It can be difficult to do both unless spend a lot of time messing with the dado blade setting (and there for the jig, unless it is fully adjustable), unless you make "Center Keyed" box joints (a symmetrical joint) like those possible with the INCRA I-BOX where differences are driven to the center of the joint. The two boxes on the left in the second row (and a few of the special splined joints) were made with the centered-keyed procedure.

Look at the joints in this pic of I-BOX joints. All boxes are made with A-B joints as I described above:

http://www.ncwoodworker.net/pp/data/2404/medium/boxes2.jpg

[Brian Brightwell]

I made these jigs for three different size joints. Moving the pin toward or away from the blade determines the tightness of the joint. The pin is adjustable on my jig and is made from key stock.

http://i773.photobucket.com/albums/yy11/bebrightwell/th_DSC_0095.jpg (http://s773.photobucket.com/user/bebrightwell/media/DSC_0095.jpg.html)

http://i773.photobucket.com/albums/yy11/bebrightwell/th_DSC_0096.jpg (http://s773.photobucket.com/user/bebrightwell/media/DSC_0096.jpg.html)

http://i773.photobucket.com/albums/yy11/bebrightwell/th_DSC_0091.jpg (http://s773.photobucket.com/user/bebrightwell/media/DSC_0091.jpg.html)