Box joints...what am I doing wrong ?

[Jay Schwartz]

I recently bought a Freud SD208 dado set and after several attempts at making box joints I find that all sides just do not line up...I have tweaked the settings on the blades, indexing pin and space in-between and still have problem. I've also tried my router table with brass set-up guides and the Rockler box joint jig and have the same problem with all four sides fitting together. Sometimes a second pass after slightly moving the jig helps but then I end up with one side that is way off...what is wrong ? Appreciate any comments:confused:

[mreza Salav]

Box joint is a VERY sensitive to extreme accurate setup. If you are off by a few thounsands then they won't fit. Without knowing your setup it's hard to tell what the solution is...

[Justin Ludwig]

Posting some pictures of your setup will help determine where you are making a bad adjustment or setup.

[Jay Schwartz]

thanks for your input...yes, I guess I'll have to keep trying till I can tell where my settings are off...they make it look so easy on youtube with homemade jigs !!

[Mike McGrath]

Jay, the easiest way to make box joints is on a router table with an Oak Park style box joint jig. You can also make angled joints with ease.
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[Bill Adamsen]

Box joints are easy once you figure out the "shift" ... it's a bit of calculation and ultimately ... trial and error. That set (Freud 308) should work (I have a 25 year old version) but my recollection is that it leaves grooves on the bottom of the cut. No matter it will work.

The "alignment peg" needs to be the same size as your kerf, and it needs to be able to adjust right and left until you find the right spacing. Once you get it right you are done until you change the kerf.

There are numerous tutorials on the web (search for finger joint of box joint) and of course many ways to accomplish the same end result.

Why don't you post a photo of your jig and detail your process and perhaps we can spot where you are going wrong.

[Ken Fitzgerald]

I have had good success using my Freud stacked dado set and a jig I made for my miter gauge. It's important that the "pin" be the exact same size as the miter blade's cut and that the distance from the cut in the jig to the "pin" be exactly the width of the pin and cut.

Do a little research.

[Mike Schuch]

I made my own sled style box joint jig out of scraps. Instead of a pin I just used a little scrap of wood that I cut after I cut the pilot slot in the jig. I made the scrap a tight fit to the pilot hole before mounting the scrap to the sled. My scrap wood jig makes nice tight box joints but only in a single finger width. Sometimes I think homemade jigs are superior to expensive store bought jigs.

[John Gustafson]

Ken has the answer to your problem. Box joints can be a pain until you get the jig exactly right. What happens with the common home built jigs is that the error is additive as you progressively cut the kerfs. if you are off say .002 at the first one, by the time you get to the seventh, you are off by almost 1/64h. Trot down to HF and get a vernier micrometer or a digital. Something that will measure down to .001 at least. Keep the width of the kerf and the space to the pin as close as you can measure. Then when you cut, ALWAYS reference off of the same face of the pin.

[glenn bradley]

Keeping your parts oriented correctly is important as well. Starting from the same edge on all pieces when cutting. I often cut oversize blanks and trim to final width.

[Al Launier]

Be sure to have the mating pieces exactly the same width. Mark the mating sides/edges to avoid this potential error. Cutting pieces oversize, as Glenn noted, and then trimming to final width, even planing to final thickness will help.

[Lee Schierer]

When I make box joints I cut the corners that will be joined at exactly the same time. They are clamped to my jig with one side offset by the thickness of the finger. Once I dial in the jig, joints go together just fine.

When you apply the glue you have to assemble the corner quickly as the glue will swell the wood slightly making the fit too tight.

[Brian Henderson]

Without knowing exactly what your jig is like, I can't really say. Box joints are really finicky, they have to be exact, any slop and it won't fit together properly. The pin has to be absolutely identical to your kerf and the distance between the pin and the blade has to be perfect too. It's kind of messy to set up, but once you have it, box joints are pretty simple to do.

Exactly how are they not fitting together? Do the first couple of teeth line up and it gets progressively worse from there? That's a measurement error that is becoming exaggerated as you move down the line. It could be either that your dado isn't exactly the size it says it is supposed to be or your pin is allowing slight side to side movement. Also make sure that your saw blade is exactly at 90 degrees to the table. Otherwise, as people have said, pictures help.

[Terry Beadle]

On the other hand.....
You can cut box joints by hand with a dove tail like saw, coping saw, and chisels. Worked that way for over a thousand years, no warranty either....hoot!

I use a Incra fence system with a straight bit. Easy. Accurate. Comparatively expensive though.