How Can I Economically Join 3-Way Corners in Open Boxes Without Screws Crossing?

[DaveC426913]

TL;DR Summary

How can I make these joints better?

I find myself making a lot of things that are open boxes - plant stands mostly.

Sometimes the wood is merely 3/4 x 3/4 nailing strips. I use deck screws to hold them together. In that case, I only use one screw, not two. (I predrill with a countersink bit or it will certainly split the wood.) Today, I made a few using 2/2s, so I used two screws, to ensure strong joints.

My trouble is, when I make a 3-way joint, the screws cross and I've busted a lot of drill bits. I try to stagger them but it's (literally) hit and miss.

Do woodworkers have a better - yet still economical - way to join these 3-way corners?

I know I could use strapping or angle brackets if I really wanted to sidestep the whole problem, but that's expensive and time-consuming. And I'm trying to make these fast, cheap and with a minimum of extra bits like brackets.

 

[berkeman]

What's an open box? Can you post a couple pictures of what you are building?

What tools do you have available already to do this work? Do you have a table saw? Or maybe just a circular saw or a jigsaw or a mitre saw?

Have you used any woodworking joints in the past?

https://toolstoday.com/learn/18-woodworking-joints

Paging @phinds

 

[hutchphd]

I am seldom happy with screws into end grain.
Why are these open frames?? For building a box, I usually use a box joint. Less fiddley than a tapered mortice.

 

[jack action]

Use wood dowels instead of screws:

​

Some ideas for 3-way corner joints (at 12:25, the dowels idea is used again (may even be screws), and at 14:54, another joint that could be done with dowels or screws instead of the square part at the center):

​

 

[phinds]

Dave, there are a TON of joinery types on my joinery sub-gossary. Lots of good suggestions above, and here are a bunch more. Find one or two that suit you and your tools.

joinery

 

[DeBangis21]

@phinds that's an excellent comprehensive list. Good!
I come to know dovetail just recently from another forum.

 

[DaveC426913]

What's an open box? Can you post a couple pictures of what you are building?

Indoor plant stands - 3/4"x3/4". These take me less than an hour to build.

(Those tops are simply deck tiles, which cost less than 3 bucks each and come in packs of 10 )

Outdoor planters 1½"x 1½". (With fence board panels) These took about 3 hours each.

What tools do you have available already to do this work? Do you have a table saw? Or maybe just a circular saw or a jigsaw or a mitre saw?

I have a poor man's workshop. Old and 2nd hand stuff.
Circ saw, chop saw, 16" planer, belt sander, etc. There's prolly a router and jigsaw around here somewhere. (I'm not sure I want to get involved in routing for this level of project.)

Have you used any woodworking joints in the past?

No.

For building a box, I usually use a box joint. Less fiddley than a tapered mortice.

The 3/4" wood is way too small for any kind of mitred joints. Though the 1½" is prolly OK.

Here is a 3/4" join:

And here is a 1½" join (you can see where I hit a cross-screw, snapped a drill bit and had to re-drill):

Use wood dowels instead of screws:

Some ideas for 3-way corner joints (at 12:25, the dowels idea is used again (may even be screws), and at 14:54, another joint that could be done with dowels or screws instead of the square part at the center):

Dowels might be a solution, though it doesn't really solve the 3-way join problem directly.

Dave, there are a TON of joinery types on my joinery sub-gossary. Lots of good suggestions above, and here are a bunch more. Find one or two that suit you and your tools.

Thanks. I knew I'd hear from you. :)

(Boy, I wish I had a dado head cutter to cut the lengthwise grooves for those outdoor planters. I had to run them through the table saw about eight times to get the 1/2" groove cut...)

(Also, fence boards make terrible slotted panels. They have a strong tendency toward "cupping", which makes it very challenging to slot them into the grooves.)

Anyway, problem with those joineries is that they might be more complex (and therefore time-consuming) than I'm hoping for. In some cases my wood is too thin for any kind of joinery. And it might be a losing battle, considering the cheap wood I am using.

This isn't fine cabinetry I'm attempting here. I'm using pretty rough wood. It has twists and knots that I have to live with. The nailing strips aren't even all the same thickness! I don't want to dramatically increase the time it takes me to build these things.


So here's an example of my situation: I could prolly add carpenter's glue to all these joints for strength, but

1. because of the wood and imperfect tools, my joints have fair bit of play. (I'm using jigs and clamps now, but still...), so glue won't be as effective, and
2. I'm impatient. It would kill me to glue a couple of things and then wait for 24 hours for it to dry before continuing (something that def had an impact on my plastic model building days or yore).

 

[phinds]

Glue small triangular pieces in each corner with superglue. A minute or two to cut the triangles and another minute or two to slap them in place w/ superglue, all for a set of 8 (each corner, both directions).

 

[berkeman]

chop saw

Can you set your chop saw at a 45 degree angle to angle these butt joints so both cross members are supported by the vertical member?

 

[Nik_2213]

As a DIY cat-gym builder, may I compliment you on those 'lounging shelves' ? I've fitted garden wall with a dozen shelves of decking as square tiles or side-by-side grooved planks, allowing multiple route options...

FWIW, for 'rough' wood-working, I must highly recommend the mentioned 'cross-dowel' approach to end-grain. It prevents / stabilises cracking and splitting, can also salvage near-Gordian 'knotty' problems...

( An unwritten 'Murphy Law' corollary is that any batten set against brick wall will have a quorum of 'knots' clash with optimal fixing locations: I've become adept at recursively cross-drilling and gluing 8mm dowels... )

 

[DaveC426913]

Can you set your chop saw at a 45 degree angle to angle these butt joints so both cross members are supported by the vertical member?

View attachment 346445

Yes. Although I don't see how that solves the problem. I'm not worried about supporting weight so much as making a solid joint that doesn't flex. And that change would still have two screws intersecting.

 

[DaveC426913]

Glue small triangular pieces in each corner with superglue. A minute or two to cut the triangles and another minute or two to slap them in place w/ superglue, all for a set of 8 (each corner, both directions).

Yeah, this may be what I do. But screws, rather than glue.

 

[Averagesupernova]

I have a poor man's workshop. Old and 2nd hand stuff.
Circ saw, chop saw, 16" planer, belt sander, etc. There's prolly a router and jigsaw around here somewhere. (I'm not sure I want to get involved in routing for this level of project.)

Old planer can often be better than new planer. Anything older that can plane a 16 inch wide board is not likely too bad for quality. I guess that depends on your definition of old.

 

[phinds]

Yeah, this may be what I do. But screws, rather than glue.

Why screws? I didn't mean don't screw the joints, I thought you were looking for extra stability AFTER you put in the screws, to avoid racking. With these supports and superglue you could use fewer screws.

 

[DaveC426913]

Why screws? I didn't mean don't screw the joints, I thought you were looking for extra stability AFTER you put in the screws, to avoid racking. With these supports and superglue you could use fewer screws.

Well, the primary problem I'm trying to solve here is finding room in the joint for all the screws without snapping my drill bits, so added braces won't fix that (Oh I see. You said use fewer screws).

My experience is that glue just doesn't hold up well to torsional forces. But maybe I'll give that a try on my next build and see how it goes.

I have a staple gun that can hold tiny 1/2" brads. I could use those to supplement the glue.

 

[phinds]

If you sand the edges of the triangles smooth and use medium weight superglue, it's essentially as good as screws.

 

[jrmichler]

Here's an idea. Two screws from each cross piece into the triangle piece, plus one long deck screw through the triangle piece into the leg. And glue all joining surfaces. Everything is securely fastened, so there should be no wobbling even without the glue. The glue is then backup for the screws.

 

[berkeman]

Two screws from each cross piece into the triangle piece, plus one long deck screw through the triangle piece into the leg.

How are the crossmembers supported by the vertical leg in your sketch? Sorry if I'm missing the obvious.

 

[jrmichler]

Each crossmember is rigidly attached to the triangular piece by 2 or even 4 screws. The leg is pulled into the square corner formed by the ends of the crossmembers by a long screw through the triangular piece. Pulling into the corner locks the leg against wobbling, the screw locks it against sliding, which supports the table. If all mating surfaces are flat and square, the resulting joint is rigid. Gluing the joint is not necessary, but adds redundancy and helps prevent the screws from loosening.

 

[berkeman]

As you know well, I'm a little slow. What is that center square in the sketch? Which crossmember does it belong to? It's the top of the vertical member, but is there overlap with one or two of the crossmembers?

 

[jrmichler]

If a picture is worth 1000 words, two pictures should be even better. Photo below shows the crossmembers and triangular piece without the leg:

Then the leg is added:

This is a two minute model slapped together from the scrap box. If I was doing it for real, the triangular piece would have the grain parallel to the 45 degree face (the long face) (the hypotenuse of the right triangle face).

 

[berkeman]

So the vertical weight forces of the load on the platform will 100% be supported by the screws between the horizontal members and the vertical support? Why not push the horizontal members a bit onto the vertical support?

 

[Averagesupernova]

That is not unlike how chairs are assembled.

 

[DaveC426913]

Yeah, maybe what I'll do is put a little 45 brace in there - not a big one like jrmichler suggests; I'll make it out of the same wood: so 3/4". And glue it and tack it with little brads. That's doesn't add too much material or time/effort.

 

[Baluncore]

Go composite.
I would replace all horizontal wood with a light strip of galvanised steel. Make a 90° fold along the top and the bottom to give the 'C' section directional rigidity to the legs, and to bear the top-load. Cut or bend corners at the fold ends to make space for legs. Short screws, through the sheet, would go into the external flat faces of the legs. The same system can be used for the lower, or intermediate shelves. The face of the 'C' would be between 1.5 and 2.0 times the leg width. Try phi = 1.618

Maybe you have a source of 'C' section in Al or galv iron, that can be cut and drilled without folding. Paint it, or use colour-bond shed cladding, new or used.

 

[Rive]

We used small wood shelf brackets instead of simple triangles so it had some 'look'.
Also, we had the top-short one from a wider piece, so we could spread the screws a bit.

 

[sophiecentaur]

I'm trying to solve here is finding room in the joint for all the screws without snapping my drill bits

I feel your pain. Been there. But using thicker timber and drilling at a good 'normal incidence' should avoid the problem.

 

[marcusl]

"Do woodworkers have a better - yet still economical - way to join these 3-way corners?"
Yes, but it sounds like you want to take an easy route. Here are three traditional joints for your application, from Fairham, Woodwork Joints. I would hold them together with a water-resistant glue (Titebond III, e.g.).

As noted above, screwing into end grain doesn't hold very well. You can insert a crosswise dowel and screw into that for better holding power. I don't have a picture but this metal version gives you the idea:

 

[Nik_2213]

IIRC, the truncated right-angle of wood or metal through-fixed from hypotenuse to leg is one of the standard ways to craft a 'storable' table.
Here's pics of a complete kit and a 'roll your own'...

 

[DaveC426913]

IIRC, the truncated right-angle of wood or metal through-fixed from hypotenuse to leg is one of the standard ways to craft a 'storable' table.
Here's pics of a complete kit and a 'roll your own'...View attachment 346544

Yes, if I were going to go this route, I'd stock up on these little guys:

but I'm trying to avoid such extra bits being added to the cost, weight and aesthetics.

 

[Nugatory]

For that sort of three-way joint, if you're making them in any numbers a plate joiner (aka biscuit joiner) is far and away the easiest answer. Of course a real cabinet maker (the kind who can cut dovetails by hand) would be making mortise and tenon joints, but the plate joiner creates joints just as strong with a lot less work.

 

[Housey210]

TL;DR Summary: How can I make these joints better?

I find myself making a lot of things that are open boxes - plant stands mostly.

Sometimes the wood is merely 3/4 x 3/4 nailing strips. I use deck screws to hold them together. In that case, I only use one screw, not two. (I predrill with a countersink bit or it will certainly split the wood.) Today, I made a few using 2/2s, so I used two screws, to ensure strong joints.

My trouble is, when I make a 3-way joint, the screws cross and I've busted a lot of drill bits. I try to stagger them but it's (literally) hit and miss.

Do woodworkers have a better - yet still economical - way to join these 3-way corners?

I know I could use strapping or angle brackets if I really wanted to sidestep the whole problem, but that's expensive and time-consuming. And I'm trying to make these fast, cheap and with a minimum of extra bits like brackets.


View attachment 346416

 

[Housey210]

From experience, depends on tools. Joiner by trade so fully equipped workshop. Mortice and tenon would be a traditional way into leg but if this something of a hobby and knocked up in a shed then a mitre joint for 4 top rails, top frame, would be a choice. Mitre increases glue line area, a biscuit, as shown by others, aids location and assembly and that joint could be held by air nail/pin. If no air tools then ratchet straps work fine, though attention to keeping top fram square is a must. When I first started out, limited tools, I found "corrugated fasteners, 'dogs' or 'wriggly nails' across mitre very good and strong, angled so pulls up. Once top frame done I guess a screw down into leg would be ok, though I would prefer a fluted wooden dowel pin. Air nail / pins leave a tiny hole easily filled unlike a screw head. If you could standardise the stock then a jig would help. What machinery do you currently use

 

[DaveC426913]

If you could standardise the stock

The stock is 3/4" nailing strips. Heavily knotted and warped. About as far from standard as one can get. But very cheap.

then a jig would help.

I try to use jigs when possible. For this, I have angle clamps.

What machinery do you currently use

A drill with a counter-sink bit, deck screws, and a chop saw.

I really wish I could use my table saw, but it blows my breaker every time I start it up.

 

[Baluncore]

I really wish I could use my table saw, but it blows my breaker every time I start it up.

Get a variable frequency drive. That will limit the startup current, or can be programmed for a slower speedup.