Help - Box Joints!

[Nathan Odle]

After some sanding, I have some box joints on a jewelery box that look like this (click pic to enlarge):

http://img139.imageshack.us/img139/6701/boxjointssd1.th.jpg (http://img139.imageshack.us/my.php?image=boxjointssd1.jpg)

Unfortunately, these aren't the beautiful, seamless box joints I had hoped for. I did these with a 6" Craftsman dado and aluminum box joint jig. I made many test cuts to get the jig set up just as best as I could, and I checked squareness and clamped the piece to the jig before every single cut. What I'm saying is, with the equipment I have I don't see being able to get much more accurate than this.

So I have two questions:

1) Is there a way to fix these joints without rebuilding the box? I was thinking about making some filler out of sawdust and wood glue, and hoping that the oil finish will pretty well disguise the rest. Does anyone think this will work? Any other suggestions? This is a Valentine's Day project, and I don't think I'm going to have time to rebuild this box so if there's a way to salvage this I would be very happy.

2) How *do* good woodworkers get those beautiful seamless joints, anyway? Does it really take a super-expensive jig and $300 dado set? Aside from setting up the cuts to be as precise as possible and checking square all over the place, are there other techniques that I need to know about?

Thanks for any help you guys can provide :)

[Mark Singer]

It is just all in the jig. They should come out nearly perfect. It is possible to cut small filler shims from the same wood. This is not the best approach. I have a jig I made that is dead on and the results are excellent.

[Greg Funk]

I agree with Mark's assement regarding the jig. I've built a couple of box joint jigs and for whatever reason the joints have come out perfect on the first try. I cut a test slot with the dado setup and then machine a piece of hardwood that fits the test slot perfectly. I then cut the hardwood up into a few pieces and then use these pieces for an index pin and a width gauge to determine how far to offset the index pin. How did you make your jig?

Your joints look like they have two problems:
1. Pins and slots are different widths which can be addressed by fixing the jig.
2. Not clamped tight enough. You should have your clamps or clamping blocks offset from the pins to squeeze the joints tight. You will need to do some planing or sanding after the glue dries to level the pins.

For a jewelry box I would use the first box as a prototype and make a new one. It will probably be faster than cutting a bunch of thin wedges, glueing them in and resanding.

Greg

[Anthony Whitesell]

Be sure to use a backer board behind your piece to pevent the chip out I see.

If you have a wooble style dado, I you leve them a little shallow and glue sandpaper to a board that is as thick as the pin and sand them to fit. The wooble Dado isn't the best for box joints.

Try making a finer (narrower pins and slots) to take out some of the issue due to the dado blade.

[Mike Cutler]

After some sanding, I have some box joints on a jewelery box that look like this (click pic to enlarge):

http://img139.imageshack.us/img139/6701/boxjointssd1.th.jpg (http://img139.imageshack.us/my.php?image=boxjointssd1.jpg)

Unfortunately, these aren't the beautiful, seamless box joints I had hoped for. I did these with a 6" Craftsman dado and aluminum box joint jig. I made many test cuts to get the jig set up just as best as I could, and I checked squareness and clamped the piece to the jig before every single cut. What I'm saying is, with the equipment I have I don't see being able to get much more accurate than this.

So I have two questions:

1) Is there a way to fix these joints without rebuilding the box? I was thinking about making some filler out of sawdust and wood glue, and hoping that the oil finish will pretty well disguise the rest. Does anyone think this will work? Any other suggestions? This is a Valentine's Day project, and I don't think I'm going to have time to rebuild this box so if there's a way to salvage this I would be very happy.

2) How *do* good woodworkers get those beautiful seamless joints, anyway? Does it really take a super-expensive jig and $300 dado set? Aside from setting up the cuts to be as precise as possible and checking square all over the place, are there other techniques that I need to know about?

Thanks for any help you guys can provide :)

1. I'm sorry, but I would do them again. It reeally sucks to tell you that, and if you made it sound like it wasn't such an important project, I'd tell you to look at Mohawk Finishes epoxy filler sticks.

2.) No it does not take a $300.00 dado stack. Freud makes a Box Joint Cutter set. They usually retail for about $75-$100 bucks, but I always see them on the discount table.
They're pretty limited in what they do, 1/4" and 3/8" box joints, but they do that very well. Perfect for jewlery boxes and smaller, finer projects.

I see two immediate problems in your picture of the joint. First, the blade is a few thousanths too high, and second, it doesn't appear that you are using a backer piece of wood. To do really fine box joints, the backer piece needs to be clamped tightly to the actual work piece so that the exit is as clean and crisp as possible.

Some of those joints look OK, but the one in the middle looks like something slipped. Does your miter bar move at all in the slot? If so. it needs to have absolutley no play or it will play heck with your work.

As for the setup. Make a test cut and measure it with a micrometer, not a ruler. Set the distance from the index block on the jig to the blade for the exact measurement taken with the micrometer.
Because the errors are additive, it really does take this precise of a setup.

The joint really isn't that bad looking, so don't get down on yourself.

[Anthony Whitesell]

Question for you Nathan. What kind of tablesaw do you have (make and style)? How tightly does the miter gauge fit in the miter slot?

[Greg Hines, MD]

The box joint jig that I use on the router table eliminates the need for making sure that your dado is set up shimmed exactly the same each time. It is simple to make, and repeatable.

Doc

[Chris Barnett]

Really cool. Click on the picture to enlarge, and you get advertisement popups and music. I hope this is just from SMC and not the post.

[Bill Huber]

I will tell you I tried and tried to get good looking box joints with the table saw. I still do not know why I could not get them the way I wanted but I just could.
I like you would cut test joints that looked good but then when I did the finial the didn't look that good.

I got the Porter Cable 4212 Dovetail jig and with in two test cuts I had a good looking box joint. Now it did take a little long on the dovetails...

[Jeff Bratt]

Two problems are visible in the picture:
a) there are gaps between some the fingers - vertically
b) there are gaps between the fingers and the board on the right.

a) is caused by inconsistent cutting of the the fingers - some are too narrow
b) is caused by either blowout during cutting or not clamping well enough to close the joint. Fixing all four corners (by inserting little pieces of wood to fill the gaps) will range from tedious to impossible.

I really like the jig detailed in Shop Notes #62. I have pics on my web page -
http://home.san.rr.com/jeffnann/WoodWorking/Shop/Shop.html

This kind of jig (with an indexing pin) has two critical components. The size of the sockets (notches) is determined by the size of the cutter - dado stack or router bit. The sockets need to fit smoothly and snugly over the index pin. Then the size of the fingers is determined by the spacing between the indexing pin and the cutter - this distance needs to be finely adjustable, stable and repeatable to insure good fitting joints.

Other considerations - to avoid blowout, use a backer board to support the workpiece as the cutter exits, and, if using a dado stack, it needs to cut a flat bottomed slot. My cheap dado set does - a good sharpening can make a decent dado stack cut well.

The final thing to consider is whether to cut the fingers so they are initially recessed or proud of the adjoining board. It's a personal preference thing, but I think recessed fingers makes it easier to clamp the joint together. Othewise you really need some cauls with a "comb" pattern that matches the spacing of your fingers to really clamp the joint tight. Either way, you plane the sides afterwards to level everything out.

With good fixturing, box joints can be made that fit perfectly every time.
Hope this helps!