bigredc

This a test leg to a coffee table base. the finished one will be walnut. I'm worried that since the grain is going the wrong way for the tenon it might snap off. It's a 1" X 1 1/2" tenon so there is plenty of glue area. I was thinking about reinforcing the tenon with a dowel. I don't want to see it though. Another though was to make a whole new tenon like what festool domino jointing system uses. Any thoughts on this?

cabinetman

Nice looking base. If you get a good fit, and sufficient glue, and allow the dry time, you should get a good joint. It does represent a weak joint for the direction of the grain.

I might go with a good size dowel.

Daren

If I used a dowel, it would be small, so as to not remove too much of the meat of the tenon. If you kinda look at that base and think about the forces that it will be under that joint is not as weak as I first thought when I circled it on the picture. You have down force, but there is some surface area on the top of the leg to take that. I was worried about racking, but looking at it again since the base is in an X and legs are diagonal it won't be direct side to side force which could shear the joint.
I think you will be ok, it is a coffee table right. Under normal household conditions (you don't have a pack of wild boys do you , they can tear up anything) it should be fine.

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bigredc

I guess someone would have to fall against it on an angle. Like you said to rack it. Just brainstorming, if you could get a piece of wood with a knot in the right place so the grain wrapped around it, and lay out the leg in just the right spot. that would be neat. Or is that just stupid and wouldn't work. It would probably only take me a few years to fine 4 of them.

woodman51jfk

I'm going to agree with the dowel, hardwood, the same diameter as the tenon, just as insurance. Use a good grade glue & allow plenty of set-up time, as was stated earlier. Nice work, and I like the half lap in the stretchers, those will also help prevent any racking.

bigredc

I practiced doing the whole joint.

Youngman

It certainly is a good looking base. The joints strength can be compromised, as you say "if someone falls on it". If the joint was made on the vertical portion of the leg rather then the horizontal the stress would be compressive rather then tensile

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bigredc

It would be more visable that way. I like the idea of it being up under the top. It occured to me to swap the joints. Put the mortis on the leg and the tenon on the other piece. Twice as much wood on the week point. I have another thread started for this project. "My first real project" in general discussion. I'll keep that one updated if anyone cares.

mmwood_1

I think this joint situation may be over-theorized. I've made joints as such in the past. I think you'll be surprised at the actual strength of this joint, in practice. I don't think you'll have a problem with it. Just don't make your tenon too thin. 1/3 the wood thickness is a general rule of thumb.

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edp

If I was to make any suggestion at all, I would suggest that the top (bearing) surface be cut at a bit of an angle so that the weight seen by the legs is over full length grains eliminating the fear of snapping off the horizontal member. Nice looking joinery.

Ed

bigredc

I stress tested the leg. it held at over 20 lbs. broke at 32 lbs. an inch before the joint.

Daren

Awesome, this is like an episode of "mythbusters" http://dsc.discovery.com/fansites/my...out/about.html , experiments in the woodshop.

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Youngman

It is like a case of Mythbusters, the weight that was being applied was only 6 inches away from the break, how much would it take if the weight was 18 inches from the joint? This is a good thread, not only on structure but on design.

Daren

Doesn't matter, there will not be any down pressure that far from the joint (it is part of a table base, not a shelf bracket) 18" is in the middle of the table.

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Youngman

Put a glass top on it and it would matter,

mmwood_1

Given the breakage, if you want to go back to the drawing board, you can make new legs of similar design, but have your vertical piece and your horizontal piece meet at the corner. Do a mitered mortise and tenon joint on them, and you eliminate the problem of short grain weakness. I've used this joint on picture frames, and some cabinet door frames.

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bigredc

The first one was a scrap 2x6. I'll be using walnut. I'm sure it's even stronger. I was stressing the crap out of it the way I hung that load. Just for S&G I put 1-- 5/16" dowel in a piece of pressure treated (more scrap) it held like 40 lbs. Then I put the first one back together with 2-- 5/16" dowels. That held the over 30 Lbs. (I didn't try any more) The picture with the bucket hanging from the leg was actually after it broke, and I glued it back together with the 2 dowels. The first one broke before I thought to take a picture. I bet once that frame is done it will hold 200 lbs. on the table, on it's own, no dowels. I'm happy with it. I did manage to use part of a knot to get the grain to wrap around the corner on 2 legs. I don't know if it's stronger I guess it can't hurt. More pictures on "my first real project"

Joe Lyddon

This is getting interesting...

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Joe Lyddon

You might get some good ideas from this...
Unbreakable Miter

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bigredc

I saw that. I have a bunch of woodworking books. That was in one. Check out this other thread. This project continues here. help with first real project