Recommended size dominos for 8 ft farmhouse table aprons to legs

[brownaddesign]

I will soon be building a couple of 8ft x 3ft farmhouse tables that will consist of 2x4 aprons attached to 4x4 legs, similar to this photo for reference:https://www.etsy.com/listing/1129443429/free-shippingfarmhouse-harvest-style

What size dominos would you use to attach the aprons to the legs?

Would (2) 10x24x50 dominos for each apron-to-leg joint be sufficient?

I'm trying to decide between the DF500 and XL700 (these tables will be the largest projects I plan on build anytime soon).

Thanks!

 

[c_dwyer]

Sure, but it really depends on the thickness of the apron, in my opinion. I just finished building a smaller version with 2, 10x24x50 dominos for each connection.  Any thicker domino would have been more than 1/3rd the thickness of the apron. The idea is to have at least the same amount of wood on each side of the domino as the domino thickness.  If your apron is 2" thick, then you can go bigger, but keep in mind whether you'll have a lot of use for a XL700 vs. DF500.  Most folks that have both indicate they use the 500 a lot more.  I'm in that camp for sure.

And welcome to the FOG!

 

[ChuckM]

If the attached sketch describes your situation correctly, you can use double twin 10x24x50 tenon for each joint using a DF500:

[attachimg=1]

Something like this:

[attachimg=2]

It is a very [size=36pt]strong[/size] joint.

If 10mm is too big for the thickness of the aprons, use 8x22x50.

 

[Crazyraceguy]

I don't know about this one?
You say "2 x 4", meaning literally soft wood (Pine, spruce, etc)? That is really only 1 1/2" x 3 1/2" and I don't think that is going to support leg connections like this without some kind of stretcher down lower.
Sure, it can be assembled that way, but it won't survive daily use. Side loading or someone trying to drag it across a floor, might not work out so well.
The connections are only as good as the wood. Domino strength doesn't matter if the soft wood fails.
The much longer Dominos of the DF700 might give it a fighting chance, just because of the greater glue contact with the soft wood. I'd bump up to the 14mm at that point too.

 

[ChuckM]

I don't know about this one?
You say "2 x 4", meaning literally soft wood (Pine, spruce, etc)? Snip.

I took his 2x4 and 4x4 to mean the dimensions, not the softwood kind found at big box stores.

 

[brownaddesign]

Sorry, yes to clarify, I meant 2x4 and 4x4 dimensional lumber (kiln-dried pine/spruce) from my local lumber yard, so 1 1/2" x 3 1/2" aprons into 3 1/2" x 3 1/2" legs.

I had considered a lower stretcher, but I want to keep the two ends open and was hoping the corner bracing for the legs and adding 3 crosspiece supports between the aprons would help keep it pretty solid.

 

[brownaddesign]

If 10mm is too big for the thickness of the aprons, use 8x22x50.

Do you think a double twin tenon using 8x22x50 would work in a 1 1/2" x 3 1/2" apron?

 

[ChuckM]

In that case, you need to use appropriately smaller dominoes for the double twin tenons. But as crazyraceguy pointed out, the lumber is weaker than beech (dominoes), and that'd be the weakest link gor the joints.

 

[ChuckM]

If 10mm is too big for the thickness of the aprons, use 8x22x50.

Do you think a double twin tenon using 8x22x50 would work in a 1 1/2" x 3 1/2" apron?

Let check it out, and get back to you.

 

[Michael Kellough]

Using softwood without lower structures to reduce the leverage of the legs you’ll need to reinforce the leg/apron joint regardless of the kind or quantity of tenons.

Something like this.

 

[smorgasbord]

I would not double the tenons across the 1.5" width.
I would, however, double the tenons across the 3.5" height (vertically).

The 12mm tenons are 26mm wide (tall in this case). With a 3.5" apron height, you would then have slightly under ½" of spacing between the dominos and between the dominos and top/bottom of the apron.

Since this is softwood, I'd go with the slightly smaller 12mm tenons (beech way stronger than your pine), and like [member=58857]Crazyraceguy[/member] says, go full depth (about 2.75") on the DF700. I suspect the domino mortises will intersect each other, but that may depend on whether you're centering the apron on the legs, or just setting them back a ½" or so. I think the latter would look better, too.

Another idea is to add material to the ends of the aprons on the inside, making them thicker. If you did the ½" setback thing I mention above, then you could add another whole 1.5" thick piece to the back inside of the apron, say 5" long. Then you'd have a 3" thick apron intersecting a 3.5" thick leg with ½" setback on the outside/front, and you could double-double stack 12mm tenons.

 

[brownaddesign]

Using softwood without lower structures to reduce the leverage of the legs you’ll need to reinforce the leg/apron joint regardless of the kind or quantity of tenons.

Something like this.

Yes I was going to brace the corners similar to this pic to reinforce the leg/apron joint.

View attachment 1

 

[brownaddesign]

I would not double the tenons across the 1.5" width.
I would, however, double the tenons across the 3.5" height (vertically).

The 12mm tenons are 26mm wide (tall in this case). With a 3.5" apron height, you would then have slightly under ½" of spacing between the dominos and between the dominos and top/bottom of the apron.

Since this is softwood, I'd go with the slightly smaller 12mm tenons (beech way stronger than your pine), and like [member=58857]Crazyraceguy[/member] says, go full depth (about 2.75") on the DF700. I suspect the domino mortises will intersect each other, but that may depend on whether you're centering the apron on the legs, or just setting them back a ½" or so. I think the latter would look better, too.

Another idea is to add material to the ends of the aprons on the inside, making them thicker. If you did the ½" setback thing I mention above, then you could add another whole 1.5" thick piece to the back inside of the apron, say 5" long. Then you'd have a 3" thick apron intersecting a 3.5" thick leg with ½" setback on the outside/front, and you could double-double stack 12mm tenons.

I was going to set back the aprons 1/2" so at a 2.75" depth they should be 1/4" away from intersecting, correct? Is that OK or does that weaken the leg/joint by coming that close?

I'm not sure I could add another 1.5" piece to the back inside of the apron at the joint because I'm doing a corner brace there for added support.

 

[RussellS]

I think the double twin Dominoes of 10mm would be great.  Four 10mm Dominoes in each rail end.  1.5 inches thick is 38mm.  3.5 inches tall is 89mm.  10mm Dominoes are 10mm thick, 24mm wide.  And 50mm long so you get 25mm, 1 inch, into each end of the rail and 1 inch into the post.  Double twin of four Dominoes would look like this:  6mm wood, 10mm Domino, 6mm wood, 10mm Domino, 6mm wood.  Side to side.  And top to bottom the two rows would be:  14mm wood, 24mm Domino, 14mm wood, 24mm Domino, 14mm wood.

Now, some might say the 10mm Domino is too thick.  Because the wood is only 6mm thick going side to side.  I think 6mm, 1/4 inch, is thick enough.  But if you don't like that, then you can easily substitute 8mm Dominoes.  Then it would be: 7mm wood, 8mm Domino, 8mm wood, 8mm Domino, 7mm wood.  Little better.  7mm instead of 6mm.

Both 8mm and 10mm thick dominoes are available in 50mm lengths.  The 8mm Domino is 22mm wide.  The 10mm Domino is 24mm wide.  Minor difference.

Using 4 Dominoes ALONG with your corner braces in the picture above, you will have a more than strong enough leg apron joint.

 

[Cheese]

Something else to consider, if the standard radiused edges don't aesthetically work for you, the 2x stock will become 3-4 mm smaller if you remove them.

 

[Packard]

I don’t use the Domino system, but when I was building a door in 1-1/2 thick poplar, I used 1/2” x 2” dowels.  I staggered the placement.  That allowed the dowels to maintain a reasonable distance from each other and from the edge of the stock. 

I don’t know if staggering is a reasonable strategy for dominoes, but it worked out well for the dowels.

Staggering allowed me to use more dowels than a single line would have and placed them off the center for greater stability.

Jessem shows that strategy in one of their videos.

 

[ChuckM]

If 10mm is too big for the thickness of the aprons, use 8x22x50.

Do you think a double twin tenon using 8x22x50 would work in a 1 1/2" x 3 1/2" apron?

The answer is yes. Here is a simple math-free trick I use to determine if any placement or combination of dominoes is good for a particular joinery situation: Lay out the joint, and place actual dominoes on the measured sketch to visualize the tenons vs the joinery:

[attachimg=1]

[attachimg=2]

You can see here that your table can be handled by the DF500 (with no issues regarding the 1/3 placement rule) using the proper tenon configuration. In your case, even the 10mm tenons will work (but given that your plan is to use softwood, I'd recommend the 8mm tenons for the double twin tenons).

This is not to say that a DF700 is not good for you, which is a good machine for really big jobs, such as huge outdoor benches or large exterior doors. I only have the DF500 because I don't do any outdoor projects and my interest is in cabinet and furniture making, and the DFXL is simply too heavy for everyday use in my case.

 

[Crazyraceguy]

Yeah, if you do it with the big metal brackets that [member=297]Michael Kellough[/member] suggested, you should be fine.
Those things can be used as "knock-down" hardware, so the Domino strength is a non-issue at that point.
I still wouldn't go dragging an 8' table around from one end, without a lower stretcher, but that's just me. Probably wouldn't do it with one [big grin]