DF 500 Domino Joins for Farmhouse Table hold up 500 lbs?

[gliu07]

Hi,

I'm new to this DF 500. I've been thinking about building a farmhouse dining table like this RH one with the marble top. The marble dimension is 96x40x2 inches. I don't know the actual weight of the marble but I'd imagine it's around 400 lb.

I plan on using 4x4 for the entire build, legs and beams to support the marble top. And using joins with dominos. How many and size of dominos should I use for each of the joins? Will it be study enough to support the weight plus folks leaning on it?

Best

 

[Svar]

Marble top this size will be 750 lb (340 kg).
I'd go with traditional mortise and tenon.
If you do want to use DF500 you'll probably be fine with 6 largest dominos per joint.

P.S. While 750 lb seems like a lot, it's a weight of 4 people. For comparison, think how beefy you'd make a garden bench for 4.

 

[Birdhunter]

I agree with Svar re traditional mortise & tenon. My gut feel is that any of the 500’s tenons are inadequate to handle the weight. I think the 700’s larger tenons would work, but not the 500’s. Putting a bunch of small tenons into the structure might weaken the wood too much.

 

[gliu07]

Thank you both for the feedback. The marble is hollowed out underneath, not a solid piece. I don't think it weights up to 750. If the angled legs will cause an issue then I might consider putting it upright instead. Will hardwood make the joints/wood integrity stronger?

 

[Svar]

Thank you both for the feedback. The marble is hollowed out underneath, not a solid piece. I don't think it weights up to 750.

Good, even less problematic.

Will hardwood make the joints/wood integrity stronger?

Yes. Dominos will definitely work then, IMHO.

 

[ChuckM]

Hardwood is far better than 4x4 material. If I were to build this table, I would use my DF500 with twin dominoes (10mm x 24mm x 50mm) where applicable, given the structural design of the legs.

 

[JimD]

I assume you are worried about the leg to apron joints.  At least that is what would bother me.  With the DF500 you are limited to 10mm thick (about 3/8 inch) tenons that go about 1 inch into each piece.  Both those dimensions are small for the application but the depth is the bigger concern.  I have a DF700 and would use a regular loose tenon, not a domino, as wide as the material allows.  I would also go deeper but you cannot. 

Vertical weight doesn't stress that joint at all.  Leaning on the table will but I think the worst is moving it around by sliding it.  You are unlikely to lift it.  If it will rarely be moved and you are extra careful it might work. 

I've unsuccessfully used biscuits and pocket screws for this joint.  So now I use as big a tenon as will fit. 

 

[gliu07]

Thanks for all these pointers! Much appreciated. Once it's in the dining room, it's not going anywhere. So here's what I'm thinking from everyone's feedback. I'll use hardwood instead. I'll use straight legs to take care of the vertical weight and to eliminate the shear stresses of the angled legs. I will use lap joints on the two beams (4x4) going the length of the table to connect to the two legs at the top and the bottom. Then add two aprons (2x4?)on the side of the top beam to support the table top. And definitely use twin dominoes.

 

[butzla]

Hardwood is far better than 4x4 material. If I were to build this table, I would use my DF500 with twin dominoes (10mm x 24mm x 50mm) where applicable, given the structural design of the legs.

No question this method will work.  I built a porch swing 10 years ago out of white oak using double dominos as ChuckM shows.  This was right before Fine Woodworking released a test over which method of joinery was strongest and the Domino scored the weakest which had me worried.  It's best to carefully cut the slots at the same narrow width setting so the domino sits tight in there.  I've had well over 400 lbs swinging on this seat and today the joint is just as tight as the day I built it.

 

[Svar]

It's best to carefully cut the slots at the same narrow width setting so the domino sits tight in there.

Exellent reminder! For structural joints - narrow setting.

 

[rvieceli]

I’d also keep the angled braces from the bottom runner to the top of the leg assembly to prevent racking.
Ron

 

[JimD]

I would not use regular dominos for this, I would cut a mortise half an inch or so narrower than the apron.  If the apron is 3.5 inches wide, a 3 inch wide mortise in the leg and the apron.  Then I would cut a piece of scrap to form the tenon.  It will take a little more time but will add significant strength.  I use my domino in a shop with a table saw and planner handy so making the tenon stock is easy.  If I did not have the table saw, at least, I would use multiple dominos. 

Last weekend I cut slot mortises nearly 6 inches wide with the 14mm cutter for a crib I'm making.  It is easy, it just takes multiple plunges. 

 

[Jesse Cloud]

If you are using 4x4 legs, you will have plenty of room for double tenons.  I would use double tenons whether I went with standard tenons or Dominos.  Don't place them too near the top.

The FWW article that Jim mentioned used a single tenon where obviously two would have been much stronger.  They did that because they thought double tenons would have been too much trouble for traditional methods.  Not really fair to Domino.

 

[JimD]

I agree with Jesse that joint tests have been unfair to dominos.  They tested really small domino joints to bigger traditional mortise and tenons and, guess what?  The smaller domino joint was weaker.  You need to get the domino joint up to about the same long grain to long grain surface and the strength will be the same - or possibly a bit better due to the good fitting domino joint.  But Matthias Wandel tested loose versus tight mortise and tenon and the looser joint was actually a big stronger.  So maybe just the same.

But this is what bothers me about a 1 inch penetration Domino joint for a leg to apron joint.  Even if you get a couple in you do not have the same joint area as a traditional joint 3 inches wide going at least 1.5 inches into the leg.  Regardless of how you get it, you want maximum long grain to long grain gluing area.