Date: 24-09-17  Time: 08:35 AM

Author Topic: Box Joints  (Read 328 times)

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Offline Michael (the Dodd)

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Box Joints
« on: 2015-07-06 02:07 PM »

So, I just finished making a box joint jig using plans very similar to these:
http://www.popularwoodworking.com/projects/tablesaw-box-joints

My only previous experience making box joints was using the Porter-Cable 4212 jig, pictured here:

It performed pretty well, but I hard time getting just the right fit-  there's no fine tuning to be had, and the difference between kinda sloppy and too tight depends on which side of the jig's "fingers" you apply pressure on.  In the end, I opted for "too tight" and pounded the box together with the biggest hammer in my shop. The plywood I was using to make the box ended up getting kind of split up and shredded in places, so I had to do a lot of extra sanding and patching with 2-part epoxy and I had a lot of problems to cover up with a dark stain so it really wasn't an optimal result:


Most woodworkers actually use a jig like the one in the first link (or some variation therein).  The idea is that it's a sled that you run through your tablesaw blade (or dado stack) that uses an indexing pin the same width and offset as your blade width to make a nice joint that fits together snugly. 

I finished mine last night- here are my thoughts in handy list format:
  • The thickness of the "key" is pretty crucial to the fit.  Since my sled was designed to make box joints the thickness of my combination blade, I was able to test the fit against the kerf in the jig.
  • Many of these sleds are not adjustable for a nice fit.  This is a mistake.  The design above lets you dial in the perfect fit, which is *crucial* to getting a nice snug joint.  I spent about an hour dialing mine in and I'm glad I did.
  • I believe you can cut a both pieces of the joint at the same time if the key is long enough.  I wish I'd used a longer key.
  • It's really important to make sure your workpieces are flat.  Any cupping in the stock can translate into joints with gaps in the fingers.  If there's a twist in your stock you might be able to strongarm the pieces together and beat them into shape, but your life will generally be easier if you get your stock right in the first place.
  • I planed the wood for my key down in my surface planer to get it close, then used my random orbit sander to dial it in.  I probably could have saved some time by using my benchtop belt sander.
I've only done test cuts so far, but I'll post a picture of some "real" work with my new jig as soon as I've got a finished project.

Offline Michael (the Dodd)

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Re: Box Joints
« Reply #1 on: 2015-07-06 02:07 PM »
Apparently this:
http://www.incra.com/product_rtf_ibox.html
Is the new hotness when it comes to box joints.  It's about 160 bucks, but it's one jig that can cut a variety of sizes of box/finger joints without the need for multiple inserts or anything like that.