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Box Joint jig

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I've managed to find a number of small instruments for my metalworking hobby - micrometers etc. for very good prices but usually without a box.

(photobucket link:

As you can see one has the original box (a very nice starrett with all the attachments) but the remainder do not.

The starrett boxes (at least this one) have box jointed sides with a tacked on bottom and sliding top.  Quite simple and they don't take up much more room than the micrometer.  A closer view of this one:

I've wanted to build an accurate box joint (sometimes called a finger joint) jig for some time but didn't get it done.  I plan to use it on my tablesaw as it's convenient and accurate (and less noisy than the router).

I did some searching around and found the one designed by the proprietor of  It can be seen here:

It's a very nice jig and seems to be an improvement of Lynn's boxjoint jig.  Lynn's jig is based upon the travel created with a 16 thread per inch rod and this gives quite fine control.

I wasn't sure I needed to get that complex so kept on looking.  Eventually I found this youtube video - a modified Lynn's boxjoint jig and it appealed to me as being fairly simple and easily modified if I choose:

Take a look at all the tools behind Ed when he is talking in the video - unbelievable.

I also found the plans that Ed posted here:

Be aware that there are a few measurements posted that are wrong.  Fortunately I found the errors before cutting any wood.

The finished jig (looking from the back):

Left side view:

Right side view:

I made a few changes as follows:

- installed bearings in the plywood ends to support the threaded rod.  It's 3/8 in. 16 tpi.
- made a threaded insert for the wood piece at the back of the carriage.  It's epoxied into the wood so isn't going anywhere.
- changed the handle to a wheel and indexed it every 10 degrees.

The reason for the indexed wheel is that for small joints (eg. 1/8 in. fingers) I will use a single blade and I don't have one that's exactly 1/8 in.  so I can use the indexed wheel for an extra cut to bring the gap between the fingers to exactly 1/8 in. (or other dimensions if I need to).

I've just built a small box out of some rather crappy plywood but plan to make some out of better material.  Will post the results when I have one or two made.  I did find that once the distance between fingers is worked out it is quite easy to use.


Thanks John for this post. My son is into woodwork and as I get to go help I found the topic very interesting. Pity the chap in the second video didn't have his camera closer but hey, we got to see his stuff PLUS the background tooling. Oh and his plans.
John B

The idea of wooden jigs and machines is very interesting, good on you for having done it! You made me think of Matias Wandle at Woodgears who has incorporated wooden gears into his box joint jig amongst other things. His gear generating program is very useful too, not only for wooden gears!

Thanks again, Matthew.

Glad to help gentlemen.

I've spent too much time on the website.  He is quite ingenious and uses wood for things that I would have thought wouldn't stand up without metal.  It's caused me to reconsider some jigs and machines.

I will post a bit later about his 16 in. bandsaw (wood frame) that I have purchased the plans for.  I've started making the odds and ends of pieces and have a motor for it.  I currently have an import 14 in. bandsaw that works ok but it's resaw ability (5 1/2 in.) isn't that great and it bugs me that some parts are difficult to reproduce when they break.  If I build it I can fix it.

Here is a link to info about the bandsaw:


naffsharpe (Nathan):
Until I finally bit the bullet and bought an Incra Jig I used the jig described by Jeff Greef on his website. It's great for finger/box joints when making the type of box you're talking about. The only problem with it (and the reason why I bought the Incra Jig ) is that you need a different size jig for each thickness of finger/box joint. Also the Incra makes me lots of brownie points



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