Thread: Domino 500 furniture specs

Hi Smithy

Basically, a domino does one of two things in a piece of furniture

ONE. if the joint is long grain to long grain, the domino helps with keeping the joint aligned when you glue it up, but in practical terms adds little if anything to the joint's strength. The joint's strength comes from the glue bond along the long grain to long grain joint faces.
Yes, you can devise a load test that demonstrates that a long grain to long grain joint with dominos is stronger that an equivalent joint without dominos, but the key phrase is "in practical terms". A well made long grain to long grain rub joint, especially on stuff 45mm thick is plenty strong enough to support a truck and I don't know of any table or furniture joint that is called upon do do that.

TWO. for butt and mitre joints, the domino acts as a loose tenon in a conventional mortise & tenon joint. The basic rule of thumb for mortise & tenon joints is that the tenon should be around 1/3 the thickness of the rail and about 2/3 the rail's height. But, when the furniture rail is 145 x 45 structural hardwood, that rule can be ignored. I'd feel comfortable with a tenon 1/5 to 1/4 the rail's thickness and 1/3 to 1/2 the rail's height. Without doing the sums, those dimensions would equate to one or two 10 x 50 dominos.

Bear in mind that timber bridges are decked with 145 x 45 structural hardwood and your settee doesn't need to support a Mack truck.

Originally Posted by gpsmith

Are there any specifications for the loads of the dominoes especially the 10 by 50s?
Would a double row of 10 by 50 dominoes every 100 - 120 mm be strong enough for the butt and mitre joints?

Regards,

Smithy you could do this which should be strong enough, or you could have two rows of staggered one up one down every 100mm .
I have the 700 as well and all that would offer would be depth & size of domino,your DF500 should suffice with the stated dominoes.
Cheers

If you are worried about their strength put one in every 20mm instead of 100mm apart.

Thanks you Ian and Johnno,
Your advice is most comforting and reassuring. I was pretty confident that it would be strong enough - but the more you read the more you doubt.
I have also seen in one of the Festool brochures a mitre joint with a pair of domino "rows" going across a fairly wide bench? but I just wanted reassurance for a settee.

Thanks once again,

A bit more information for you

Rick Christopherson's "supplemental user's guide" http://www.waterfront-woods.com/fest...ino_DF_500.pdf -- references the US model but otherwise a very good read.
(copied directly from Rick's guide)

When the strength of your workpieces is comparable to the strength of the Domino tenon (e.g. general hard woods) then the thickness of the Domino tenon should be approximately 1/3 the thickness of the workpieces. (This is the rule 1/3 rule of thumb I mentioned above.)
► It is acceptable to use a tenon that is slightly thicker than 1/3 when the width of the Domino tenon is relatively narrow compared to the width of the joint. This is why 8mm Domino tenons are the most common for joining ¾-inch lumber.
► For softer woods, such as pine, the joint will be stronger when the tenon is 1/3 or slightly less.

Domino Tenon Placement Guidelines
There are no steadfast rules on where tenons should be placed, especially when they are used for alignment purposes. For edge joining boards, a typical placement might be 6 to 8 inches apart.
However, when tenons are used to strengthen a joint, you might be tempted to place the tenons too close together. This can actually weaken the joint by removing too much of the substrate material.
► A wide mortise weakens the substrate, so it is better to have several narrow mortises with uncut space in between, than it is to have a single wide mortise with several tenons side-by-side.
► When placing several tenons close together, leave at least twice the tenon thickness between mortise holes. As a general rule, this means the minimum tenon spacing should be about 10 mm to 20 mm, but they can be spaced much wider.
► When creating stacked mortises for extra thick lumber, an extension of the “1/3 rule” mentioned above still applies. Specifically, the distance between mortises, and the distance between a mortise and the wood surface should all be equal to (or larger than) the thickness of the tenon.


To which I'd add BUT ...
145 x 45 hardwood is the size of stuff used for structural timber framing. It is far far stronger than necessary for furniture, so some of your joint dominos will be placed to stop a joint twisting as you put it together, and your slots will need to be elongated to allow for seasonal movement