Multi tenons in attaching a leg to a table top (end to face)?

[walkman]

I'm building a large table and I want to join a 3"x3" leg to the bottom of the table using tenons for extra strength.

How can I position the work so I can get a stacked tenon? 

Everything I've seen has been doing a single tenon approach for something like a shelf in a bookcase. As far as I can tell I can't use the normal fence offsets when working with a face.

 

[Jesse Cloud]

Hey Walkman.

I'm not sure that tenoning the leg to the tabletop is the best way to go.  Couple of issues: running a tenon into end grain will make the leg want to split along the grain when it is stressed - not sure this would actually be a strong joint - and usually you want the table top to be removeable, especially on a large table, so you can move the table later on.  Typically we use "z-clips", buttons, or figure 8 hardware to attach the top to the aprons.

If you really want to do this, I would place the top on the base and draw the location of the legs on the top.  Then you could mortise the legs using the same face on each leg consistently.  Then measure where the mortises actually are, and mark that on the tabletop.  Use that mark to make the mortise on the table top.

 

[Jerry Work]

Hi Walkman,

From your post it is not clear to me what you are trying to do.  Does your table have aprons connecting the legs or do you want the top to sit on top of each leg by itself (not nearly as strong)?  

If it has aprons, connect them to the legs with Domino M&T joints for strength.  Then just domino mortises into the inside of each apron to create a step about on 10mm below the top edge of the apron and cut step blocks to match.  Put the tongue of the step block into the domino mortise and screw the step block to the underside of the top.  This is a very strong construction and will accommodate any movement if the top is solid wood.  The aprons will reinforce the legs to prevent them from racking.

If you want to just attach legs to the under side of the top, select one edge and the leg center line as the reference points.  Draw that line on the under side of the top and position the domino relative to that line and a centerline for the position of the leg.  The base to center line of cutter on the domino machine is 10mm and the base is marked with a center line and several other reference lines making it easy to cut several mortises on either side of the leg center line.  Use those reference lines to place as many mortises in the under side of the top where you want them.  Use the center line and reference edge of the leg and then offset the Domino machine fence to put the centerline of the cutter where you want it to match the mortises cut in the underside of the top.

Just note that no matter how strong the M&T joint is at that point, it will not withstand much rack force and the legs should be braced in some way.  I hope I read your post correctly and this is the kind of answer you are looking for.

Jerry

I'm building a large table and I want to join a 3"x3" leg to the bottom of the table using tenons for extra strength.

How can I position the work so I can get a stacked tenon? 

Everything I've seen has been doing a single tenon approach for something like a shelf in a bookcase. As far as I can tell I can't use the normal fence offsets when working with a face.

 

[walkman]

Thanks for the replies -- sounds like it would take careful measuring and placement. I was hoping for an easy "registering" method.

I'm building a torsion box table so I'm not incorporating aprons, etc. I was thinking of mortising the leg to the face of a plywood plate & then screwing the plate to the table (that's how I'll make the legs removable). To help with the racking force I was thinking of attaching some bracing to the plate around the leg.

 

[Markus K.]

I'm building a large table and I want to join a 3"x3" leg to the bottom of the table using tenons for extra strength.

How can I position the work so I can get a stacked tenon? 

Everything I've seen has been doing a single tenon approach for something like a shelf in a bookcase. As far as I can tell I can't use the normal fence offsets when working with a face.

that won't work for a long Time. I've made 2 Tables, 7' x 3', and one 4' by 4'. I made it like Jerry subscribed: I used aprons (5" by 1"), in which I pushed in the Legs. They are fixed with one 8mm screw. This is more then enough to tighten the Legs to the Apronframe. The Tabletop is mounted like Jerry's solution.

Here you can see the Screws in the Legs (they're upside down) and the tabletop with the apronframe, witch is made with 8 pieces. You can remove the legs easily by unscrewing them!

 

[greg mann]

Regardless of the wisdom of one construction technique over another, and I will gladly defer to Jerry on that, if you are intersted in stacking dominos accurately I have a method that I just used yesterday that worked very well. Pick the spacing that looks close to what you want for your first row. Make a spacer that will fit between the fence and one of the 5mm pins. You may want to alter the setting just a little to conform to a convenient spacer you already have, i.e., 3/8" instead of 10.5mm. Set the fence using that spacer and make your cuts. Then add another spacer to establish your second row. In my case I had a reveal between the 2 elements so I used a .531 block and a 1.003 for one piece, a .216 and a .688 for the other. The important thing was the constant .472 difference in each case. This kept the domino spacing equal. I have a set of machinist's gage blocks so that makes it a little easier for me but you can do the same with some hardwood blocks or brass set up bars.