# Is this going to be strong enough?



## CrankAddict (Dec 10, 2018)

Hi Everyone,

Very new to woodworking and still ensure of how to design things that require actual strength. I'm looking to build a table like this:










30" high, 42" diameter glass top. The glass itself will probably be 70lbs, so the legs definitely need to be able to hold some weight. I'm thinking of making the legs out of 1 5/8" thick stock, perhaps walnut. I've seen a commercial version of a similar table that appears to use dowels to secure the upper and lower leg parts:










It also has a metal brace attached to the bottom of the X. I'd like something that is strong enough using all wood, no metal. I was thinking about a tenon that went into a mortise in each leg piece kinda like this:










Would that be as strong or stronger than the dowels? Or is there some completely different technique I should be considering?

Thanks!
Jeff


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## MPython (Nov 30, 2018)

That looks plenty strong enough to me, much stronger than dowels. If it were me, I might pin each section of the uprights to the tenon just to be on the safe side.


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## redlee (Apr 11, 2016)

I think the way you have drawn it will be fine, 17 1/2 lbs per leg and add a Turkey and fixens I doubt each leg will have to support 30 lbs each which is minimal for your design. Until someone sits on it then !!!!!


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## Kazooman (Jan 20, 2013)

One thought is to be certain to make the mortise and tenons as deep as you can (within reason, of course). The bulk of the strength in the joint will be be from the faces of the tenons. The end grain joint of the legs and the leg assembly to the cross pieces will be weaker. Any weight on the table will be trying to spread the joint apart, pivoting on the inside corner of the joint.

I like the table design. I would recommend spending the money to get a top made with low iron glass. That eliminates the dark green color regular glass would have at the edge replacing it with a nice light blue.


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## SMP (Aug 29, 2018)

Maybe draw bore them, rather than the way they have them, to keep them nice and tight.


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## Phil32 (Aug 31, 2018)

Mortise & tenon joints are strongest where the loads are at a right angle to the tenon. The angle of the legs, both to the floor and the top, would tend to separate the joints. The area of glue surface may be greater than dowels, but I question joining three pieces with a single mortise & tenon as with each leg.


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## pintodeluxe (Sep 12, 2010)

I'll bet those are screws with tapered plugs to cover the hole.

I would be tempted to build it that way too. My reasoning is this… mortises are going to be difficult to cut on those angled legs. However, with a handheld router and edge guide it could be done.


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## BlueRidgeDog (Jan 2, 2019)

You are not using all the long grain to long grain glue up area you could get out of the joint. I think if you made the tenon taller, near stub level, you would get a stronger joint…that and four pegs and you would be good to go.


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## Unknowncraftsman (Jun 23, 2013)

I agree with Pinto those are plugs covering screws.


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## CrankAddict (Dec 10, 2018)

Thank you to everyone for the helpful feedback. Based on what I think I'm hearing, I have modified the tenons to extend out further, to be full height, and to have pins. Is this roughly what all of you were describing?


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## BlueRidgeDog (Jan 2, 2019)

> Thank you to everyone for the helpful feedback. Based on what I think I m hearing, I have modified the tenons to extend out further, to be full height, and to have pins. Is this roughly what all of you were describing?
> 
> 
> 
> ...


With a tight joint, that should be solid. IMHO!


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## JohnMcClure (Aug 24, 2016)

The experts here have weighed in and know much better than i do, but I dont understand why each leg is made from 2 pieces. If you have wide enough stock available, the top and bottom leg parts could be one piece, thus stronger.
If you don't have wide stock, you could glue some up. More waste this way, but less chance of failure?
Either way post it as a project when finished, and if it ever breaks post that too so we all learn!


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## CrankAddict (Dec 10, 2018)

> The experts here have weighed in and know much better than i do, but I dont understand why each leg is made from 2 pieces. If you have wide enough stock available, the top and bottom leg parts could be one piece, thus stronger.


I'd be curious to hear more about this as well. Somewhere I read that with a 2 part leg you want the grain to run straight in each leg piece for maximum strength, which is what you'd get here. It would also waste less and allow for narrower stock to be used as you said. With legs this long that is a pretty dramatic difference. By my measurements it would require 10.25" wide stock to cut them out of a single piece, but only 3.25" wide stock for the 2-piece version.


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## bilyo (May 20, 2015)

I understand and agree with the need for the largest tenon possible. However, if I was the person doing this, I would want to allow for a bit of error in cutting the mortise. With the tenon the same height as the rest of the horizontal member (no top or bottom shoulder), if the mortise is cut slightly taller than needed for the tenon you will end up with a small visible gap. I don't think a small shoulder at the top and bottom will affect the strength of the joint by much and will ensure that a small gap will be covered.


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## CrankAddict (Dec 10, 2018)

> With the tenon the same height as the rest of the horizontal member (no top or bottom shoulder), if the mortise is cut slightly taller than needed for the tenon you will end up with a small visible gap. I don t think a small shoulder at the top and bottom will affect the strength of the joint by much and will ensure that a small gap will be covered.
> 
> - bilyo


That actually makes a lot of sense. Especially at this point in my woodworking journey, I shouldn't be opting for any techniques that require "perfect" cuts. Even a 1/8" shoulder on top and bottom should provide a safety net for me.


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## clin (Sep 3, 2015)

I think you about have it. I agree that using a single piece of wood for the legs would weaken them. I think the angle is a bit too much in this case.

I would consider a few other things. One is thicker stock. 1 5/8" seems a bit narrow to me. If that photo is 1 5/8", it does look right.

Another idea is to add two pegs. As you have drawn it, the peg looks like a pivot point. Obviously the shoulders would prevent it from rotating, as should the glue. But two pegs would create a very positive joint that would remain strong should the wood shrink and the joint loosen, even without any glue. Though I would still glue it.

The middle looks like a half lap. It looks like the piece, with the notch in the top, would try to spread and open up the joint. While I know you don't want this, a metal strap across that on top would provide that support. Just not sure how you could get some tensile strength across the top of that piece. Maybe embed a spline across the top.

My guess is there is something you could do that would be a bit stronger. But, just because something can be stronger, doesn't mean it's not strong enough.

I like the design and look forward to see your finished project.


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## BlueRidgeDog (Jan 2, 2019)

Agree…you don't want a stub tenon, you need some shoulder.


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## Phil32 (Aug 31, 2018)

The setup for mortising the legs is going to be challenging, especially if you make them one piece.


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## sras (Oct 31, 2009)

Cutting the mortise would be simplified if you went with a through tenon. Then you can cut the mortises straight through the legs.

The tenon could either be exposed or trimmed flush.


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## bilyo (May 20, 2015)

> The middle looks like a half lap. It looks like the piece, with the notch in the top, would try to spread and open up the joint. While I know you don t want this, a metal strap across that on top would provide that support. Just not sure how you could get some tensile strength across the top of that piece. Maybe embed a spline across the top.
> 
> - clin


I was also thinking about that lap joint. Considering the size of the member, I will likely be OK. But, I think a spline across the joint both top and bottom would be an improvement; unless the OP decides to include the metal strap.

Looking at the picture of the commercial version, I wonder if those plugs cover up some through bolts.


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## pontic (Sep 25, 2016)

Split dovetails on the legs let into the cross pieces.


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## CrankAddict (Dec 10, 2018)

A few of you have mentioned the center X piece wanting to spread open on the top. Thinking about this more, the lower leg pieces are longer and splay out farther, so I would think they would actually tend to lever the *bottom* open more and if anything squeeze the top closed. All of that comes from assuming the total load on the table would be shared by the upper and lower legs, not simply acting on the uppers. But I'm not a structural engineer either 

In any case, I was thinking that I could perhaps do an elongated "bowtie" type of spline/insert like I see people put on live edge table tops spanning a crack. I don't know the real name for it, but it would seem to offer some mechanical hold beyond what a straight spline would.


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## bilyo (May 20, 2015)

> In any case, I was thinking that I could perhaps do an elongated "bowtie" type of spline/insert like I see people put on live edge table tops spanning a crack. I don t know the real name for it, but it would seem to offer some mechanical hold beyond what a straight spline would.
> 
> - CrankAddict


You could do that, but I think it would just complicate your cuts unnecessarily. A well fitted straight spline glued in place top and bottom would suffice and be much easier to cut. I also think that a straight spline would be less likely to leave weak spots due to the taper of the bowtie.

A structural analysis proving the need for all this would be interesting. Lacking that, your attention to details like this will be impressive.


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## pete724 (Mar 9, 2016)

I will let others speak for the basic joinery but if you wanted to "beef it up". You could place a wooden "gusset" in place of the metal x cross.

You could place one under the center section and another on top. They could be diamond ,square, rectangular, or round or elliptical to match the top glass!


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## runswithscissors (Nov 8, 2012)

Maybe extend the tenons all the way through, which would maximize glued surface, and peg as well. The through mortises could easily be cut with a dado on the TS.


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