Yet another box joint jig

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Forum topic by MrRon posted 10-03-2013 10:01 PM 3422 views 1 time favorited 22 replies Add to Favorites Watch
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10-03-2013 10:01 PM

Topic tags/keywords: jig

Here is another box joint jig. This one uses a piece of wood that has 1/4” holes drilled accurately through as shown in two rows. It is screwed to your miter gauge. Each row is used to cut starting pins or follow pins. A piece of 1/4” steel (or brass) rod is used to index for each cut. A hardwood will give best results when drilling the holes precisely. I have a vertical mill that I can use to drill accurately spaced holes, but a drill press may work if you can layout the holes precisely. This would be a great project to be made using metal instead of wood by someone with the requisite tools.

I told you I was retired with a lot of free time.

22 replies so far

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#1 posted 10-05-2013 07:09 PM

No one appears to be over thrilled over my latest box joint jig and I don’t blame you. It is strictly a design on paper (CAD). I haven’t built it, but I’m certain it will work. The weakness of the design is; the precise layout of the holes. If one hole is out of line .001” or .002”, the jig would not work. Because I have a milling machine, I have the capability to build this jig from metal and be assured it will work. For the masses who don’t have my capability, it might be near impossible to build this jig, even with a drill press. I don’t know what I was thinking at the time, but I must have been wearing my machinist’s hat, not my woodworking one.

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#2 posted 10-05-2013 10:32 PM

I Like the idea.

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#3 posted 10-06-2013 05:18 AM

Yup, wrong hat ;-) The first thing I thought was how will anyone get the holes accurate enough? A simple box joint jig on a sled is simple, easy, quick and accurate.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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#4 posted 10-24-2013 10:41 AM

I like the idea; as a matter of fact, I had a very similar idea a while ago when I tried a few different methods to cut box joints on a router table. Getting the holes accurately spaced is the problem. I thought of using shelf-pin jigs or similar components to integrate these into the jig.

I did end up building a jig for box joints with spacers, which would sit to the right of the piece being cut and removed according to the box joints I wanted:

This worked quite well, and was especially fun because I was able to cut box joints of arbritraty width:

But there were still too many possibilities for errors, and I got a bit frustrated :( Hence no proud post of the jig here.

Then, just as an idea, I figured why not use my Incra bend-ruler as an indexing mechanism:

I made a very simple prototype, and it actually worked quite well. I used it in a similar way as I used the spacers. I mounted the bend-rule on the vertical fence, and used a small metal shim, which itself is mounted to a “spacer board” to register into the slots of the bend-ruler.

I haven’t taken the crude prototype to it’s next level yet… instead I have been very interested in the concept of a screw-advance box joint jig, and have started to design my own. What I think is better about it is, that the part being cut is firmly mounted as opposed to being moved by hand for every cut. This ensures better accuracy. I still need to figure out some details for that before I can start building it. And then… oh no, I still have an apartment to remodel, too!

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#5 posted 10-24-2013 10:05 PM

DrTebi, You are way ahead of me. I design jigs, but rarely actually build them unless I need it right now. Your box joint jig shows how precise it can be. I have been thinking to build a jig for a project that is in my bucket and it will probably be similar to yours. Using aluminum spacers is much better than wood. I chose wood because most woodworkers can make wood spacers. I’m sure the Incra rule would work, but there could be the introduction of an incremental error. Fixed thickness spacers will index exactly every time. An error of .001” or .002” could mean the difference of a perfect fit or one that is too tight or too loose.

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#6 posted 10-24-2013 10:19 PM

Yes, aluminum spacer should work better than wood, but getting aluminum spacers that are accurately 1”, 1/2” etc. wide is either very difficult, or very expensive. I used simple bar stock, and they were all a bit off. ‘tried to lap them square, that proved to be difficult as well.

Yet I still think the problem with the spacer-based jig is, that you are manually moving the workpiece after every cut. This tends to introduce small inaccuracies. I am not being neirdy… I am just talking from experience.

It would be much better if one could design the fence out of two rails—the workpiece would be clamped to the upper rail, the spacers fixated to the lower rail. Then one would just take spacer out and slide the rail with the workpiece over… I hope that makes sense. Maybe something to draw out for you, I haven’t tried drawing that yet.

And by the way, doing this on a router table proved to be a bit trouble-some as well, because you don’t really want to plow a 3/4” x 1/2” box slot in one go—that’s why I have started to think about a box-joint jig for the table saw.

On another note, I am very jealous about your vertical mill. I would love to have one, it would be great for making jig parts, and if I had one with a high-speed motor, routing wooden parts would be very interesting and accurate too.

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4764 posts in 3240 days

#7 posted 10-25-2013 11:02 PM

DrTebi, I am redesigning my box joint jig now to index a spacer at the top of the fence. I can make it in metal, but I will try to build it with wood to see how well it works.

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4764 posts in 3240 days

#8 posted 10-25-2013 11:10 PM

Box joints are easy to make. They usually turn out perfect once you have tweeked the jig. The problem with current jigs is; they have to be tweeked every time you set up for making box joints. That can be time consumming. I am trying to come up with a jig that can be used without any tweeking.

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#9 posted 10-26-2013 01:05 AM

Mr Ron, I solved the “tweeking” problem with my shop made simple box joint jig by saving a piece of wood that I cut PERFECT box joints on. I then use this board to set my jig up every time I use it. Saves a lot of time and “tweeking”.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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#10 posted 10-26-2013 11:48 AM

Make sure to post your progress on the box joint jig based on spacers. I am curious to know how you like it.

I think I will give mine another try again soon—I just ordered a set of parallels (those used in machine shops), which I need for some other stuff, but they should make perfectly accurate spacers. I am curious to see how my results will be, and whether my earlier mentioned inaccuracies will still play a big role with very accurate spacers.

I really like the spacers concept because of the variable box-joint widths. That makes all the experimentation worth it.

I hope you will get good results. And you can always make your own accurate spacers on your milling machine, too. I wish I had one… not sure if I could justify the expense for a bench-top version…

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#11 posted 10-26-2013 07:07 PM

Ron, I had a nice Bridgeport mill at our plant in my machine shop before the plant burned down last summer. However, I still don’t think that I would have built a jig with all of these holes. It’s true that you have to tweak the typical type of jig but if you build an accurate jig that’s not that difficult. And if you have a milling machine it’s especially not that difficult. That’s just my two cents. Incremental tools has a really nice I box jig BTW.

helluvawreck aka Charles

-- helluvawreck aka Charles,

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#12 posted 10-26-2013 09:00 PM

how accurate are the holes on a peg board? Would this work as an hole templete?

-- Randy - If I'm not on LJ's then I'm making Saw Dust. Please feel free to visit my store location at

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4764 posts in 3240 days

#13 posted 10-26-2013 10:17 PM

Blackie, I would not rely on hole size or spacing of pegboard for a box joint jig. With a box joint, we are dealing with thousands of an inch. Just .001” off and it will accumulate and throw the whole joint off. The width of the pins of a box joint have to be exactly the same as the space between pins. I gues that is why woodworkers have not been able to come up with a fool proof jig.

DrTebi, This is really a machinist job. I have made box joints before using the traditional method of cutting a groove; fitting a pin; taking trial cuts and tweeking before getting it just right. I’m looking to eliminate those steps, so this is a work in progress.

What I am trying to do is to create a box joint jig (which BTW could apply to dovetail joints) that can be built by woodworkers; for woodworkers without metal skills, or metalworking machines.

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#14 posted 10-27-2013 01:35 AM

I see your point, MrRon. It makes a lot of sense to design an accurate box joint jig that can be shared with other woodworkers, who can then copy and maybe improve on the design.

Keep us updated on your progress. I am curious to see what your spacer-based box joint jig would look like.

You mentioned putting spacers at the top of the fence. I had a similar idea too, but found it difficult to fixate the spacers without them getting in the way of the workpiece.

One idea I had was to use spacers that are mounted similar to a flip-stop, below is an image of the drawing:

It would work nice, but making spacers in that shape would be very difficult, or expensive to have them made.

I also found that good dust collection made a big difference. After I added a dust shroud to my box-joint jig, I had a lot less trouble with dust that would get caught in between the spacers and the workpiece.

Also, I tried some toggle-clamps for fixating the workpiece, but eventually got rid of them and used only sandpaper on the fence. This works well, and does not really require any other clamps to hold the workpiece.

Afterall I still think that a jig with a screw-advance, similar to this by Mathias Wandel, or this one by Lynn will work best; it mostly just depends on an accurate lead screw, the workpiece is mounted and not moved manually, and it would still allow to make arbitrary width of box joints etc. Something to keep in mind/check out.

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#15 posted 10-27-2013 11:10 AM

Ron, I know exactly what you mean, I use the MLSC Multi-Joint Spacing System on the router table and I finely after countless trial, error, wasted wood parts found a method that works, I first secure the router move the guide up next to the bit then using the brass key in between both the bit and guide rail I turn the arbor by hand allowing the bit to just barely kiss the key slightly moving it forward, this I found to make great fits. I also wrote a review on this system both here on LJ's under the MLSC web site.

I just the other day posted this under another box joint topic, The key and recipe to accurate joints are.

Gap A gap between each pin and slot is caused by a key that’s too close to the bit.

Too Tight If the pins won’t fit in the slots at all, the key is set too far away from the router bit.

Offset An offset can be caused by not having the workpiece fully seated against the key.

DrTebi, thing about the jigs from Mathias and Lynn both show to use the tablesaw with a dado set, myself and goal is to do all of my joints on the router table saving me the time to swap on blades on the tablesaw, to this day I’ve not purchased a dado set and have done everything on the router table, except miter joint keys (1/4”) I’m looking for a jig that will allow for 1/4” keys on the router table until then I am only limited to what my forest flat kerf single grin blade will allow.

-- Randy - If I'm not on LJ's then I'm making Saw Dust. Please feel free to visit my store location at

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