Box joints

[kmealy]

I've made box joints a number of ways, on the table saw and router table. A couple years ago, I was making a carrying case for my wife's Singer Featherweight sewing machine. Her usual request is "Don't make it too heavy." So I used some 3/8" QSWO.

Trying to do some finger joints about 3/8" wide by the time I got to the top of the 15" box, being off just a 0.001" accumulated some error. So I gave up and did splined miters.

I got to thinking there has to be a decent way to do this. So I made some jigs using just a strip of wood cut into short pieces and attached to a base, alternating offsets. I use a flush cutting router bit and do one side on the near side of the jig and the mating side on the far side. It has worked well and if I need a different spacing, I just spend 15 minutes and make a new jig.

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[Cherryville Chuck]

Nice job Keith. I tried making one years ago and it also had a slight error. Mine was fixed so there was no correction that could be made. I think the plan came from FWW magazine. I've since seen another from them that easily addresses the problem. You still make a saw cut with your dado stack and place a key way in it. You have the option of either matching the key to the saw cut or matching the thickness of the dado stack to a key. The difference in this newer version is that the board you do this on clamps to a board attached to your miter gauge or purpose built sled. What that does is it allows to to bump the board with the key in it a nudge left or right to correct that compounding error if the fit isn't just right. You are still limited to that specific size finger with these type jigs which is why the Ibox jig is so superior if you plan on doing a lot of this type joint. It can be adjusted to any size dado stack.

FYI, a finger joint jig also doubles as a jig for making dentil molding only you don't really need the key for making dentil molding. Dentil molding doesn't need perfectly spaced and sized gaps so a stop pin is sufficient

[kmealy]

One way I've done it is on the table saw. Put a front face piece on the miter gauge and clamp it down. Cut a slot with a dado blade. Then get a piece that fits firmly into the slot. Use two widths of that piece to set the rip fence at the end of the face piece. Unclamp and move the face piece over to the rip fence without the spacers. Run a test cut. Then tweak the face piece left or right to loosen or tighten the joints. The only problem is that you almost need two table saws, one with the dado set and one with a rip blade to do this. Taking the dado set out and putting it back in might change the width a hair. The other option is to make several rips and pick the one that fits best.

[CharleyL]

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I have made many box joint jigs for the router and the table saw, but the one that is best and easiest to use for me is the Incra I-Box jig that I have now. I use it on my Unisaw, mostly with a Freud Box Joint blade pair for 1/4 & 3/8" box joints, but I also use a Freud ripping blade with FTG teeth to make 1/8" box joints, and a Freud DADO stack for box joints larger than 3/8". My box joints are near perfect every time when making them in 1/8 - 3/8" widths using these blades, and when making box joints larger than 3/8" the DADO blade set doesn't make the bottoms of the cuts quite as perfect, but with the larger joints this isn't as noticeable. For clean cuts, always use a new position of the jig's zero clearance MDF piece after getting the jig width and blade depth for what you want. Making a fresh cut in the MDF piece just before cutting the box joints pretty much guarantees clean cuts on a table saw. With a router table, the bit cuts in both directions at once, so a sacrificial second piece of MDF behind the work and clamped to it is really necessary for clean cuts.

All of my old shop made box joint jigs went to the scrap/burn pile after getting the I-Box jig and blade sets. I had many sizes, but the I-Box jig is so easy to adjust from 1/8"to about 1" that I had no need for any of them anymore, and my I-Box jig takes up less space than the pile of shop made box joint jigs. Attached are a couple of samples of box joints made using the I-Box jig and the Freud SBOX8 blade set. Who said that "You can't make box joints in plywood"?

Charley

[Nickp]

Who said that "You can't make box joints in plywood"?

At some point I will be able to say the same..."Not I said the frog"...

Perfect joints, Charley...!

[DaninVan]

Couldn't you simply have trimmed the excess off to match the low sides? ...he asks innocently.

[CharleyL]

Couldn't you simply have trimmed the excess off to match the low sides? ...he asks innocently.

Making box joint pins longer than the thickness of the wood used is a way of highlighting the joint. I actually make mine just slightly longer to account for any slight problems getting the joint really tight during glue-up. I almost always use Tight Bond Extend glue, especially on boxes larger than about 6 X 6 X 6" so I have time to clamp it better, but even that does not always work perfectly. I then sand off the excess after the glue dries for the view shown. Some like long pins and even round off the end corners. To me, it looks too much like a log cabin when this is done and I don't care for it.

Most of the boxes that I make are tool boxes or boxes to hold and protect something that I fear will be broken if not well protected. I want rugged boxes, but they don't have to be perfect like for jewelry boxes, etc. I even made a box to keep my Incra I-Box jig in. The other photo is of the box for keeping my CRB7 router jig in, mostly for keeping all of the loose pieces and options for the jig together, because I was certain to loose them if not kept together. I've developed a method that works well for this design for me and they go together very quickly.

These are all photos of boxes that I've made in the past, but I will be making more again soon. I have a need for some larger boxes for my photo equipment that I'll be making soon. About a year ago, maybe a little more, I made some "Apple Boxes". These aren't really for apples, but used by the movie and photography business as variable height platforms for things. They are 12" X 20" and a full set includes thicknesses of 8", 4", 2", and 1", so stacking them can achieve any height from 1" to 15". The name likely came from the very early photography and movie days when they gathered apple crates from a nearby grocery store and stacked them to raise a camera tripod or a person to get their shot as desired. There are Half Apple Boxes too, which are in the same height sets, but are all 12" X 10" in size. I'll be making some of these soon too.

Charley

[Herb Stoops]

Those are really nice, Charley,
Herb

[DaninVan]

Great write-up, Charley, but I meant the slight discrepancy along the top edges of the sides and ends, in kmealey's photo

[CharleyL]

That can happen between running the first "A" board cuts and then setting up for the mating "B" board through a slight error in setting up for the beginning cut on the mating "B" board. If using the square pin, and it isn't perfectly square, just a 90 deg rotation when you pick it up can cause this. Try marking the side that must face forward before cutting it free from the piece inserted and glued into the first cut of your jig, if this is the type of box joint jig that you are using.
Just a slight trim of the top edges is an easy fix for this, but a chance to learn how to avoid it the next time.

Charley

[Herb Stoops]

I hate it when that happens, sometimes I run them through the tablesaw to flush them up.
Herb

[DaninVan]

Herb! You da man with the spectacular block planes!! Using the TS is sacrilege...

[CharleyL]

I hate it when that happens, sometimes I run them through the tablesaw to flush them up.
Herb

That's the easiest way to fix it when it happens. The best way to avoid it is to assure that the spacer used to offset the "B" board when making the first cut is the exact width of the key pin of your jig, which also needs to be the exact width of your blade set or router bit (not the rated size, but the actual size when measuring it with a precision measuring device like a digital caliper), and mark it's top so you are always using it's width to space the first cut of the "B" boards. If it's top to bottom dimension isn't exactly the same dimension as the side to side dimension, using it turned 90 deg will cause the mismatch are experiencing when assembling "A" to "B". Another way is to use the first pin of the "A" board as the spacer when positioning and cutting the "B" board, but if you didn't cut the "A" correctly, you will be increasing the error. It's best to make a "Key pin for the jig that is longer than needed and then cut it shorter to make the "Key" for starting the "B" board cuts. Just remember to mark the top of it and use the width of this "Key" for starting all of the "B" board box joint cuts.

Charley

[Herb Stoops]

That is what I do too, make the key long enough to make both out of it.
Herb

[Herb Stoops]

I would like to see then make a carbide TS blade teeth shaped like a Dovetail,..........................
HErb

[Cherryville Chuck]

I would like to see then make a carbide TS blade teeth shaped like a Dovetail,..........................
HErb

I've seen stories of a few guys who had blades either modified or made so that the top of the teeth had a bevel angle equal to one of the dovetail slopes. Then they tilted the arbor to that angle so that the tooth top was level and ran the boards through, flipping the board around to angle both sides of the cut. I'm pretty sure I read one of the stories in FWW a couple of months ago.

[Herb Stoops]

[quote="Cherryville Chuck" post_id=9688 time=1639295941
[/quote]

I have seen a couple too, Chuck, But don't you think that one could be ground the shape of a dovetail so tilting is not necessary? The box joint blade is a good example. A big square chunk of carbide. Do the same for a chunk shaped like a dove tail.
Just think of all that could be done with a blade like that.
Dovetail slots for sliding dovetails, dovetail rabbits,overlocking dovetail joints for lengthwise joinery, etc.
I would buy one.
Herb

[Stick486]

that won't work Herb...

[Cherryville Chuck]

It wouldn't matter if it were ground in the shape of a dovetail, it would still make a straight walled cut. Teeth on a standard saw blade are tapered and they make straight walled cuts. The only way you get the slope is to angle the blade. Once angled the only way to mirror the first cut is to rotate the board 180. I had to think about that for a few minutes. At first the idea seemed plausible until I remembered the the teeth contact the bottom edge of the board first.

[DaninVan]

I think Herb was pulling someone's chain. (NOT Apr.1st yet, Herb!)

[Herb Stoops]

OK

[Stick486]

I think Herb was pulling someone's chain. (NOT Apr.1st yet, Herb!) :)

he does a lot of that...

[sunnybob]

I've made this one, so accurate that the pieces are difficult to fit together.
The video shows three very useful jigs, the box joint jig starts at 8:50.

[Biagio]

Bob, did you use a part of a tiling trowel like the guy did in the video?

[sunnybob]

Yes, its one of those "why hasnt anybody ever done this before?" moments.
More accurate than any casting because they are all cnc laser cut, and costing pennies.
And a bit of searching will get you different sized gaps for larger or smaller boxes.
So far I've only used it once because of other work, but the fit is impressive.

[Cherryville Chuck]

The best ideas are usually the simplest ones.

[Herb Stoops]

Bob, thanks for posting. I have a couple of those jigs, but that boxjoint one takes the prize. the ones I have require a different one for each width and uses the same set up for each tooth by moving the board instead of the gage. I like this idea better.
Herb

[CharleyL]

The main reason why I bought an Incra I-Box jig is that when you change the width of the pin it automatically changes the space to match at the same time, after the initial calibration of the jig, which is simple. I have been amazed how accurate and easy to set up the I-Box jig is. So much so that all of my shop made box joint jigs went to the burn pile. I had about a dozen of them, each set up for a different size or version. So I've saved precious space in my shop by getting the I-Box jig, since it requires so much less space than all of the shop made jigs. I can adjust it for any size box joint desired, make one test cut to be certain that I have it and the saw blade set right, move the sacrificial piece in the jig to a fresh position, and begin cutting my box joints.

The inventor of the I-Box jig is a member of NCWoodworker, the local club that I belong to. He brought his working prototype to our annual picnic and demonstrated how easy it was to use, and right there I knew that I had to have one, so I placed my order as soon as they became available, and I've been enjoying it ever since. If I need to make a box for any reason, and I can possibly use box joints for the project, the jig gets put to use. I rarely use my Leigh D4R now, unless I have to have dovetails for the coming project. I have the box joint top plate for the D4R, but making box joints with it is nowhere near as easy as with the I-Box jig. Box joints are super strong and so much easier to make now. Using the 1/8" (0.0126") Freud ripping blade makes very impressive small box joints with the I-Box jig that look great for very small boxes. I've made a few jewelry and trinket boxes this way, but most of my boxes use 1/4 and 3/8" box joints made with the Freud SBOX8 blade set.

Charley

[Cherryville Chuck]

I tried making one that was shown in an FWW article quite a few years ago. I didn't get the spacing perfect and it had no adjustment, as it was fixed to the saw's miter gauge. I've seen a newer version that addresses that by fixing a backer plate to the miter gauge and clamping a face piece onto it with the key in it. You can tap it back and forth to get the right fit then.

But the problem with that whole system is that it requires you to get the same dado stack on each time. Too narrow and the slots won't fit onto the key. Too wide and the fit is sloppy.

Like Charley I turfed my home made one and bought the Ibox. Now I just put on however many blades I want that seem appropriate for the job and adjust the jig to fit the blades.

As an FYI, I watched a guy do a rough experiment to test and see if the size of fingers made a difference in strength and there wasn't much, if any, difference from making a single 1/8" saw kerf per slot to one that was 3/8 or 1/2" He destructively tested them with a hydraulic cylinder with a pressure gauge to show how much force was being applied.

[CharleyL]

I agree, but strongly suggest that you get a Freud SBOX8 blade set or one of the similar brands. A DADO stack just doesn't make nice flat bottoms in the cuts, so desirable for the 3/8" and smaller box joints. The Flat Tooth Grind of my 1/8" Freud ripping blade works great for the smaller 1/8" box joints and I'm certain that other brands of blades also offer 1/8" FTG blades for ripping that will make great 1/8" box joints too, but I use my DADO stack when making box joints larger than 3/8", as the uneven bottoms of the cuts made by the DADO blades aren't as objectionable in the larger box joints.

[Herb Stoops]

When I had my dado set sharpened I specified to sharpen them to make flat bottom cuts, which they did and they do.
Herb

[Stick486]

When I had my dado set sharpened I specified to sharpen them to make flat bottom cuts, which they did and they do.
Herb

Same here....

[Cherryville Chuck]

I agree, but strongly suggest that you get a Freud SBOX8 blade set or one of the similar brands. A DADO stack just doesn't make nice flat bottoms in the cuts, so desirable for the 3/8" and smaller box joints. The Flat Tooth Grind of my 1/8" Freud ripping blade works great for the smaller 1/8" box joints and I'm certain that other brands of blades also offer 1/8" FTG blades for ripping that will make great 1/8" box joints too, but I use my DADO stack when making box joints larger than 3/8", as the uneven bottoms of the cuts made by the DADO blades aren't as objectionable in the larger box joints.

My Onsrud set is pretty good but I think they quit making blades a few years ago. For a while on ebay they were unloading blades and bits at fire sale prices. I picked up a bunch and I remember BJ3 saying he did too. I was getting 60 and 80 tooth miter saw blades for about $12 each I think. They cut like they're going through butter. I have 6 finger pull router bits I got for $8 each. Anybody wants one I'll sell one for $10 plus shipping.