How to join a 4-way table leg intersection?

[ryan carlino]

The base of a dining table I'm making has a complicated intersection and I'm not sure what the best way to join the 3 or 4 pieces is. Here's a pic of the model:

Table_Model.jpg

The table and its components are made of 8/4 mahogany. The legs and the feet are glued up to make them a little beefier (about 3 1/2" thick).

I'd like the long bottom rail to be a solid piece. The legs join in from the top with double tenons, similar to this:

Table_Leg.JPG

I don't have a plan for the short legs that come in on the sides, but am leaning to double loose tenons. I'm concerned that the intersection of the tenons would weaken the overall joint. I would glue the side legs in. Then make the mortises for the legs. In order for the tenons not to interfere, the sides would only have room for a single tenon (which seems really wimpy).

Table_Side_Leg.jpg

I could double them up, but they would eventually get chopped up by the tenons of the legs.

Table_Side_Leg2.jpg

Table_Leg_Tenons.JPG

I also toyed with vertical tenons in the sides, but that seemed to break up the grain flowing through the bottom rail.

How would you join these pieces? Thanks in advance for any comments.
ryan

[Ken Fitzgerald]

What about dovetails for the two cross table legs and mortise/tenon for vertical table leg?

[ryan carlino]

Cool idea! The sides could be sliding dovetails and the top leg still enter from the top with a tenon. Here's a shot with 1" and 3/4" deep dovetails.

Table_Side_Dovetail.JPG

The double tenon on the leg chops them up, but I could either move it over of go with a big central tenon.

Table_Side_Dovetail2.JPG

Proportionally, I'd probably go with wider dovetails than I drew at first and stick with 3/4" deep (long). They also don't need to go all the way to the top surface. Do you think a single, 1" wide tenon is enough to anchor the leg?

Table_Side_Dovetail4.jpg Table_Side_Dovetail3.JPG

[Yonak Hawkins]

The undersides of the feet will not be visible. Could you drill holes into the ends of the feet and through the bottoms of the legs for threaded rods and cut channels on the underside of the feet big enough to tighten nuts on the rods ? They would also tend to lock in the tenons of the legs.

[Ken Fitzgerald]

I think the 1" wide double dovetails or just 1 wide 3/4" deep one on the end of each leg would hold. With good joinery and glue it would be strong.




What about making the cross legs....1 leg and join it to the trestle portion using a half-lap joint and then pin that joint with the tenon from the vertical leg?

[Sam Murdoch]

Perhaps 1/2 lap the base cross pieces. The 2 cross rails coming up from the bottom into the center rail with the legs tenoned into the assembly as you show in your 2nd illustration.

[Brian Tymchak]

I like the idea of the half-lap that Ken and Sam have offered. I think I would use that and put a wedge in the through tenon of the vertical piece. I think that would lock it all together into 1 solid unit. To make the wedge run cross-grain of the bottom board of the lap joint, I would have the short cross piece on the bottom side of the lap.

[Sam Murdoch]

I think the 1" wide double dovetails or just 1 wide 3/4" deep one on the end of each leg would hold. With good joinery and glue it would be strong.




What about making the cross legs....1 leg and join it to the trestle portion using a half-lap joint and then pin that joint with the tenon from the vertical leg?

Sorry Ken, I read your first sentence then missed your 1/2 lap idea. Then didn't notice until I just read Brian's post. Oops!
In case you are wondering I agree .

[ryan carlino]

Thanks for the ideas so far. I have a nice feeling about the sliding dovetails being very robust, but, at the same time, a little more difficult to make. The half-lap side leg has been on my mind and I can't get past the thought that as the table top gets pulled on sideways, the forces will be transferred to the side legs and the possibility exists that you would see the joint open up. I think I am underestimating how beefy the stock is at this point, though.

In this example, the bottom rail still has 1-3/4" of material above the half lap.

BottomRailHalfLap.JPG

The side leg has 1-1/2" of material below the gap.
SideLegHalfLap.JPG

Do you think a gap would ever be see here? I'm thinking of having a face-off between the half-lap and the sliding dovetail using some scrap. It would also show me how much work each one would be to make (the half lap has to be quicker).

BottomRailHalfLapGap.jpg

I also thing the threaded rod idea has merit. However, with the big tenon coming in from above, I'd need to be sure that I plan for it accordingly.

Thanks again for your thoughts.

[Ken Fitzgerald]

Ryan,

I don't think shrinkage would be a problem as the grain runs the length of the legs in both planes.

But even if it was a problem, It would be equal regardless of the type of joinery at that joint.

As Brian suggested, if a through tenon with a locking wedge and glue of course, I think it would be strong.

Of course, having dry stable wood at the beginning is important!

[ryan carlino]

I was thinking more of kids hanging on the side of the table (and other household abuses ) causing the side leg to deflect. Since the top edge of the joint is end-grain, I wouldn't expect any glue to hold. If the half lap was too thin, I'd think the sides could flex away from the long rail.

A thicker half lap would help this, but I am also trying to balance having the base be stiff enough while not looking too chunky.

As an aside, some of the pieces have been milling really nicely (especially when the grain has a slight overall slant to it). Others, with major grain reversal, are showing the alternating smooth and torn-out feel that mahogany is known for. One section of sap-wood is downright furry after going through the planer. I have a feeling I have a lot of sanding in my future

I have the top glued up and had a local wood source run it through their 42" wide belt sander. That was the best $20 I spent on this project so far.

[Prashun Patel]

+1 on half lapping the base pieces and then making a mortise right through the center for the leg. Don't break up the base components into tenoned pieces; the half lap will make for a sturdier base, imho.

[Brian Holcombe]

For what it's worth, there is a ton of force on that joint when it's put on an angle like that. For that reason you generally see joinery that is larger than the width of the base and is integrated in a way which tightens the joint as weight is put on the table, rather than causing it to pull apart.

It also removes the chance of weakening the joinery which connects the base by having the upright connect separately to the base than at the same point at which the base is joined together with the outriggers.

There is a downward force put on the uprights when a table is in use, but also there is often a twisting force on a table in use from people pushing away from it for various reasons.

[Mike Wilkins]

How about half-laps on the stretcher and cross-legs, them mortise the joint for the uprights, like the double-tenons in your drawing. When the half-laps are glued together, the joint would be stronger than the surrounding wood. Do a trial run in some construction lumber first.

[Jason Roehl]

Thanks for the ideas so far. I have a nice feeling about the sliding dovetails being very robust, but, at the same time, a little more difficult to make. The half-lap side leg has been on my mind and I can't get past the thought that as the table top gets pulled on sideways, the forces will be transferred to the side legs and the possibility exists that you would see the joint open up. I think I am underestimating how beefy the stock is at this point, though.

In this example, the bottom rail still has 1-3/4" of material above the half lap.

BottomRailHalfLap.JPG

The side leg has 1-1/2" of material below the gap.
SideLegHalfLap.JPG

Do you think a gap would ever be see here? I'm thinking of having a face-off between the half-lap and the sliding dovetail using some scrap. It would also show me how much work each one would be to make (the half lap has to be quicker).

BottomRailHalfLapGap.jpg

I also thing the threaded rod idea has merit. However, with the big tenon coming in from above, I'd need to be sure that I plan for it accordingly.

Thanks again for your thoughts.

I like this approach, but I would swap the half-laps so that the shorter pieces sit on top of the long piece. Then, when someone puts downward force on the edge of the table, the load path only goes through one joint, and will be at a shallower angle--in other words, there's a more solid connection from the vertical support to the short side piece, and it's higher off the floor.