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In this bench, the joints appear to be simple miters; however, I can't believe that this piece would be stable with a simple miter. How might this joint be constructed so that it is strong enough to prevent racking but still appear to be a miter? enter image description here

  • There was, not sure how I managed to edit it out. All better :) – Daniel B. May 22 '15 at 5:21
  • FWIW, wood glue is really strong. – DA. May 22 '15 at 16:15
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    Yes it is, but those miters are effectively end grain, typically you want something extra to reinforce an end grain to end grain glue joint because they aren't as strong (fibers pull out, glue is sucked into pores, etc) Glue is strong, but if the joint is expected to take any kind of load, I'd do more than just glue. – Daniel B. May 22 '15 at 16:39
  • Yes, good point about it being end-grain. – DA. May 22 '15 at 16:41
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I own the bench along with the matching table. It is a simple frame constructed with 2x3,a simple reclaimed board veneer with miters.

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There are many hidden reinforcements you could use - biscuits, dowels, or more complex hidden joints such as these:

Mitred corner dovetail joint Mitred corner dovetail joint

Mitred blind dovetail joint Mitred blind dovetail joint

... but I wouldn't recommend them unless you have a lot of skill with a chisel, and a lot of time on your hands.

Both of these images are from here which is a really excellent site for all kinds of woodworking terms, and has lots of variations on common joints etc.

  • Hm. I think with a jig, the dovetails could be done by a router and just squared with a chisel. The partial miter could be done with a crosscut sled on a tablesaw? – Daniel B. May 14 '15 at 3:29
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How might this joint be constructed so that it is strong enough to prevent racking but still appear to be a miter?

It's not racking that is the major concern here, it would be (probably sudden!) failure of the glue line in one or both of the mitres.

The answers from WhatEvil and Matt cover many of the solutions. There are a number of variations on blind dovetailed mitres, but the others are of increasing complexity and hence harder and harder to make accurately.

To add some details re. splined mitres (a stopped splined mitre to be specific, also called a hidden spline mitre joint or blind splined mitre joint):

Stopped splined mitre

With the bench being made from fairly beefy material it allows for quite a substantial spline being used, as I've illustrated above. Even made from hardwood (with the grain oriented correctly, as shown) it is probably strong enough to be impossible to break in normal use, if plywood is used it would be stronger still.

Almost certainly overkill but for absolute assurance the spline could be made from metal (in which case it should be glued in place with epoxy or polyurethane adhesive).

Bonus joint: if a slight difference in appearance would be acceptable the rebated or rebbeted mitre joint could be used as well:

Rebated mitre joint

This is a significantly strong joint and may be the easiest wood-only solution as only three saw cuts are required per edge.

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    You could still hide the rebated mitre joint as well if you were so inclined. It is arguably easier to do than the hidden dovetail joint. – Matt May 14 '15 at 11:29
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    @Matt, yup you could do that but in the spirit of keeping it as simple as possible I thought I'd just mention the basic type. Thanks for the edit BTW, I see the benefit. – Graphus supports Monica May 14 '15 at 14:13
  • I'd worry a bit about the bonus joint. The lower two faces are both end-grain to long-grain joins, and I'd be a bit leary on that account. Of course, the intrinsic strength with regards to vertical force is obviously high, but I'm concerned about racking breaking the glue line. – WhatRoughBeast Dec 4 '15 at 21:54
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I've thought about this some more and have come up with an alternative solution. If I had to make this bench and be sure that the joints won't break over time, I'd want to look at some real reinforcement... how about a steel substructure?

So you have your basic bench structure which is made by lamination of smaller timber boards:

Laminated mitred bench - overall

The fact that it's made of smaller timber boards allows you to sandwich the boards around a bent steel plate:

Bench exploded

Cross section of the whole bench:

Bench cross section

Cross section through main part of bench showing steel housed within timbers, with optional dowel:

vertical cross section

Fully exploded view:

fully exploded view

So basically:

  • Get 2 pieces of steel cut and folded (which should be quite cheap from a local fabricator), I have drawn them at 5mm thick with a 60mm timber thickness.
  • Get your constituent timber pieces for lamination and groove them out using a router or a circular saw. I have shown a 10mm groove width to allow tolerance for the steel, though in reality the less tolerance you can have the better.
  • Optionally, drill dowel holes to aid in positioning / holding the whole thing together.
  • Glue the whole timber part of the bench up around the steels. I'd advise either using an epoxy glue to glue the steel into the timber and take up any tolerance, or wedge the steel tightly into the timber using timber wedges or maybe standard plastic packers or wedges, but you can get away with using PVA wood glue for the timber itself.

Now you have a really sturdy bench that looks simply constructed, and isn't actually that hard to do. If you build it right, this thing isn't breaking in a hundred years.

Bear in mind this is just a concept. You could use just one central steel, or 3 steels, or smaller, separate steel brackets at each end, or you could use biscuits to reinforce between the horizontals either side of the grooves. The basic premise is the important thing and that's to build the laminations up around steel brackets in order to add hidden reinforcement.

  • I was actually thinking about this when somebody else had mentioned using a metal spline. I think it's probably overkill, especially given how heavy steel is, but it certainly would be sturdy! I think perhaps aluminum would be a better choice. It's plenty strong for that purpose, less prone to chemical degradation, and much lighter. – Daniel B. May 15 '15 at 23:25
  • You don't necessarily need to use steel but it has a number of benefits. It is very cheap for one, the corrosion is easy to get around by giving it a coat of rust-proofing primer, which most steel fabricators can do for you (and also bear in mind that in this application it will be fully encased), and there's also a difference in that steel will bend before it breaks and is much more durable in regards to repeated fatigue and loading. To be honest, both are probably fine for such a low-load/stress item, but the cost would clinch it for me alone! – WhatEvil May 16 '15 at 11:10
  • Wood is pretty strong. This is likely over-engineering. Clever, but overkill. – DA. May 22 '15 at 16:15
  • Wood is strong. End-grain glue joints are not, especially for this type of loading, even with dovetails. – WhatEvil May 26 '15 at 9:35
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While I may (justifiably) be shunned for bringing it up, it is possible to get right-angled dowels. http://www.fastenersplus.com/90-degree-right-angle-furniture-dowel-pkg-3.html This will prevent any motion of the pieces, but it's not what you call a purist approach to woodworking.

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    You monster! :) I don't think anybody here has shown to be super purist, as evidenced by suggestions of steel splines. – Daniel B. May 15 '15 at 23:31
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Metal Brace

This is not my area of specialty at all but if I had to guess I would say that there are some metal brackets hiding underneath the joins that we cannot see. Quite possibly in conjunction with what ever joint is hiding in there.

corner brace

Just as long as they are a strong metal. Not like the cheap ones made that are zinc plated you commonly find in hardware stores. They will bend a twist without much effort.

Splined Mitre

I don't see this with a bench but you could hide a large splinted mitre, that does not transverse the entire width, reinforced with screws or bolts underneath. Graphus has the correct terminology for this joint:

a stopped splined mitre to be specific, also called a hidden spline mitre joint or blind splined mitre joint

I would be wary not using some metal hardware to reinforce this bench. Most people don't lightly rest the bottoms on a bench.

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    The "cheap ones made from zinc" in the hardware store should be galvanised steel, so it's just zinc on the surface. – Graphus supports Monica May 14 '15 at 8:45
  • @Graphus Made some updates. – Matt May 14 '15 at 11:32
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Besides mitered versions of various types of other sufficiently strong joinery methods, you could use non-mitered versions of any of those, and more (dovetail, dowels, Domino, mortise and tenon, box joints, dadoed/housed joints, knock-down hardware, etc.--perhaps even butt joints with countersunk lag screws), using any sufficiently strong material.

Then, when you're all done, veneer the whole thing so it looks like you used miter joints. This wouldn't be my first choice, but the parts of the bench look thick enough that almost any material would be strong enough. You could certainly achieve the same look with inexpensive materials, artificially-distressed veneers (even 1/8" or thinner might do it), and faux miter joints.

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