Challenging glue up - box joint tool chest

[Mike Fritz]

I tried my first box joint project today. I am building a number of wall hanging tool chests. Today I cut all the box joints for a 24" x 36" x 5" box.

I struggled like crazy on the glue up. Didn't realize with this box joint that the entire box would act like a shifting parallelogram. Every time I tried to put a Bessey clamp on the entire box would shift out of square. Eventually I had to abandon any clamps and just work like crazy to get the diagonals to match.

What could I have done better to make this joint easier to handle during the glue-up?

[Jerry Miner]

You might find it useful to use a "clamping square" to keep things square during glue-up (I make mine from plywood scraps):

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[Bradley Gray]

+1 on this. Also, If you are building a number of these the same size, you could screw some scrap ply inside corner blocks to your assembly table and clamp around them.

[Mike Fritz]

Thanks.

I was thinking about building a big square corner that I could push one corner into, but your clamping squares that I could use on all four inside corners will probably be better.

Good ideas, and impressive sketchup diagram WITH box joints!

[Bill McNiel]

IMHO - You only need one corner square, assuming you have cut opposite side equal, one 90 degree corner and equal opposite side will result in all four corners being 90 degrees. Four will require your layout/placement of the corner squares to be located/mounted "dead on". Not a necessary stress.

[Mike Henderson]

This probably goes without saying, but be careful you don't glue the square to the box. Put tape (or something else) between the box and the square.

Mike

[Charles Lent]

I always use Titebond Extend glue when making boxes with box joints. It gives you more time to glue up all those box fingers before it sets. It's white, and dries clear, so it's probably just standard white glue, but it seems to hold very well with about 24 hours cure time. I glue up and assemble all four corners before it tries to firm up on me. I can then clamp it together and square it up before the joints start setting.

Charley

[mreza Salav]

why do you need clamp at all? if your box joints are tight you simple slide them in and square your box and let it dry (same with dove tail joints).

[Ray Newman]

You did not mention the back.

A "fitted" back will square up the case. A few years ago, I built several large cabinets for the shop and cut a groove in the sides, top, and bottom to hold the back. With dovetails or box joints stopped grooves look better/will be needed. A stopped groove hides the exposed grooves. I cut the stopped grooves on a router table. The back could also be held in place with a rabbet -- builder's choice.

Then I cut the back to fit and did a dry assembly. On one or two cabinets, I slightly trimmed the back to fit and close up the joints. Glue up (applied some to the grooves) went easily and the cabinets required minimal shifting to square up. Left the clamps on for 24 hours to ensure a good glue bond.

Since a tool cabinet will hold weight and costly tools, go one step further: reinforce the box joints. In the front and back corners, center and bore 3/16" or so hole through 3 joints to accept a brass (or other metal) rod, apply a bit of glue to hole, then tap in the rod. A counter bore and wood plug will hide the metal rod if desired. The rod will prevent the joints from separating in the event of a glue failure, weight, etc.

As others posted, utilize a slow set glue. If shop-fabricating a large square, you can also trim off the 90 degree corner at 45 degrees so as not to glue it in place.

[Myk Rian]

This probably goes without saying, but be careful you don't glue the square to the box. Put tape (or something else) between the box and the square.

Mike
Personal experience? ;)

[Mike Fritz]

Thanks everyone lots of good ideas.

Mike H - whenever I see a reply with the phrase "probably goes without saying" I pay very close attention - these are usually the best tips, or obvious mistakes I'm just about to make.

Mreza S - this is my first attempt at box joints, so my joints are not even close to perfect. I figured out the problem was my cross cut sled. While making the box joints I slid the sled through the dado blade for the cut, and then pulled it back over the blade to set up for the next cut. But my cross cut sled runners aren't perfect so on the pull back I can here the blade widening the slot cut. I need to build a better cross cut sled for this technique.

I found a great video on Youtube that helped me really understand an easy way to build a jig and make box joints with tight tolerance, of course I have found many ways to not achieve tight tolerance. For anyone interested the video is https://www.youtube.com/watch?v=NutwD7B6tmE by William Ng

Ray N - good idea using the back to help in the glue up, but I want my back to be replaceable, and during my glue up I had glue pouring all over the place so the back would have been stuck permanently. Your simple idea about cutting the 90 degree corner of my squaring block to keep glue from making contact is priceless! The simple ideas are the ones I never think of - thank-you. And yes I made the mistake of not doing a stopped rabbit for the back, so I have some filling to do on the finished box.

Here is a picture of the tool cabinet I have been using for the last 15 years. It's 4' by 8' when fully open, and I have never closed it. It's very functional. But I wanted to create a more refined version now, and I've settled in on my every day tools that I want easy access to.

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I'm rebuilding it in cherry as 4 separate 2' by 4' sections. They will always be open and hung on the wall with a french cleat. Some sections might have internal swing out sections to provide two layers of tool storage. I usually wouldn't use cherry for something in the woodshop, but in this case I am reusing about 100 of my older cherry stickers I have used for years while sawing lumber on a Woodmizer sawmill. I love projects where I create something useful out of scrap wood. After a couple of days with the jointer and planer I created about 20 cherry blanks at about 48" by 5" for the tool cabinet sides.

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Here is my first 2' by 4' section with the box joints. A great learning experience. You have heard about my glue up challenges and thanks to your tips I will do the second section a lot differently. The joints were not that tight - need to build another sled. I also had some chipout around the fingers, but that's mostly because of the sticker wood I'm using. It will be interesting now to see if I can get the second section better.

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[Alan Schwabacher]

One way to clamp box joints is to use stretchy rubber tubing. It can be wrapped around not too tightly so as to hold everything together without pulling it out of square, and then each subsequent wrap increases the clamping force without pulling it out of shape. The main thing to watch out for is that glue sticks to natural rubber, so you need prevent contact with some sort of corner caul or tape. This leaves inside dimensions accessible for checking diagonals, and external clamps fit over the tubing to square the assembly if needed.

[Al Launier]

Glue-ups tend to make me nervous when there is a lot of surfaces invloved, and I sometimes find myself on the verge of panic. So, when confronted with this situation I prefer to glue fewer sections at at a time, but making sure they are square, properly aligned & clamped as sub-sections before gluing. This was suggested a few years back by Glenn Bradley & it has saved my projects a number of times (thanks Glenn). Once the separate sections are cured I'll then clamp the sections as a final assembly for final glue-up. This provides me with greater confidence knowing I don't have to fight against time constraints. This has worked well for me as I don't like to rush.

[glenn bradley]

You might find it useful to use a "clamping square" to keep things square during glue-up (I make mine from plywood scraps):

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I do as Jerry does. I also often glue and clamp one corner of each pair and then join the sub-assemblies after the first pair has set; like joining two "L's".