Domino Joint Fails

**Carry Pine** · 21st July 2007, 01:26 PM

Now that i have your attention....

I had the surprising experience this morning when 2 domino joints failed on the side table (pictured). I was sanding the legs and the joints failed where the rail meets the leg.
I know in hindsight that there is a huge amount of leverage when pressing on the leg and I should have had it supported better. I do have a few questions for the experienced Domino people:
* I used one 8mm X 40mm domino for the joint. Timber is 24mm thick. more dominoes? bigger?
* I used Titebond 111 glue which also gave way. Given that I was working in temps of less than 10 degrees, any suggestions there? I have always used white PVA in the past with bicuits, lap joints and dovetails and never had a problem.
* And here's the surprising thing. Where do you think the dominoes gave way? Pulled out of one of the mortises? No. They sheered off. They broke across the width - from the top down I presume. A clean break inside one of the mortices. Now that makes me wonder about the quality of the dominoes themselves. They are made of real wood whereas some people on the Forum are talking about making them out of MDF. I would think they would be even weaker. And I can't imagine one made of ply (like the biscuits) sheering off like that. There must be similar situations in chair making where there is a long lever that puts pressure on a single joint.

Once the table top goes on I have no worries about the tables staying together and I have learned my lesson about fulcrums and leverage. Any feedback on the choice of domino, glue or methods would be appreciated.

PS While gluing the 2 boards that will make up the tops of the tables I used the setting on the domino that allows no variation in width (you know the one on the left). I was amazed that the boards went together perfectly and all in about 5 minutes.

Graham

**martrix** · 21st July 2007, 04:14 PM

interesting. Can you show us the failed joint and the sheared off domino?

On occasion I have needed to make the domino's a little smaller so I give them a few taps with a hammer to slightly compress the grain and make it a looser fit. I have noticed that if you tap them too much, they do seem to break up quite easily......hmmmm

**Carry Pine** · 21st July 2007, 08:39 PM

Originally Posted by martrix

interesting. Can you show us the failed joint and the sheared off domino?

No, I have redominoed the joint. But i would be willing to duplicate the experiment.

CP

**jefferson** · 21st July 2007, 09:18 PM

The latest Fine Woodworking mag has a lot of interesting data on joint strength etc. so I suggest a quick read.

A couple of interesting points from the lab tests:

- nothing is stronger that a "real" mortice and tenon joint
- dominos rank well ahead of biscuits and dowels
- PVA works as well as any, including "glue starved" joints.

So I wonder what the problem was with the domino joint.

And, to be frank, I also wonder why the sanding exercise was done after glue up. Why put more stress on any joint in that way? Sorry, but that's exactly what I wouldn't do.

Also, except on coffee tables etc, I reinforce the corner joints with same size timber and screws.

As always, there may be a simple answer. Perhaps a bad domino?

I don't know. I've sat my backside on biscuit joins and waited and waited and waited for the biscuits to sheer. It never happened.

Jefferson

**Tonyz** · 21st July 2007, 09:52 PM

Sorry for this, take it as it is.
All I read was your heading and thenHA HA HA so there whos the show off now

**bitingmidge** · 21st July 2007, 10:13 PM

Originally Posted by jefferson

As always, there may be a simple answer. Perhaps a bad domino?

I think more like a bad glue joint! I haven't yet been able to get a glue joint to fail on the joint.

Sometimes it pays to wait till the glue's fully cured!

cheers,

P

**Groggy** · 21st July 2007, 10:56 PM

Graham, without being there, I suspect the glue had not set (age of glue plus cold maybe?) and the weight/leverage was all on the domino.

Can you make another one fail in the same way without the glue?

Edit: I noticed my pot of yellow glue is thickening up today, time to get some fresh stuff.

**Shedhand** · 21st July 2007, 11:11 PM

I'd be inclined to blame the glue. Age and Cold. Anyway, its better that the domino fails than the parts joined by it.

**Jedo_03** · 21st July 2007, 11:24 PM

states fairly clearly that the loose tenon broke...
QUOTE: And here's the surprising thing. Where do you think the dominoes gave way? Pulled out of one of the mortises? No. They sheered off. They broke across the width - from the top down I presume. A clean break inside one of the mortices. Now that makes me wonder about the quality of the dominoes themselves

NQUOTE

Well, I presume that the tenon grain of these 'dominoes' runs with the length of the tenon - not across it... so why did it snap across the grain...
Hellish shear force for that to occur... or a crook domino with crazy grain.
Some pics of the failed domino might yield an answer...
Jedo

**Groggy** · 21st July 2007, 11:29 PM

Originally Posted by Jedo_03

states fairly clearly that the loose tenon broke...

Yes, that was noted. But he also said that he put another domino in to fix it. If the glue did not fail then how was he able to re-use it? The timber would have split wouldn't it? Unless...he only glued the domino and not the faces of the timber itself?

So many questions....

**Greg Q** · 22nd July 2007, 10:18 AM

My bottle of Titebond III states 45 F as minimum temperature. That's what?... about 8 C ? So how much below 10 C was your glue-up?
(The glue also states max storage temp of 23 C...guess I'll have to start leaving it in the pantry).

It's possible that the failure that you observed started with a the bond, allowing the domino to fail under pure shear as the joint opened. At least that's the way that bad things usually happen to me...the house of cards effect.

Greg

**Shedhand** · 22nd July 2007, 10:35 AM

Originally Posted by gregoryq

My bottle of Titebond III states 45 F as minimum temperature. That's what?... about 8 C ? So how much below 10 C was your glue-up?
(The glue also states max storage temp of 23 C...guess I'll have to start leaving it in the pantry).

It's possible that the failure that you observed started with a the bond, allowing the domino to fail under pure shear as the joint opened. At least that's the way that bad things usually happen to me...the house of cards effect.

Greg

Wind Shear?

**Greg Q** · 22nd July 2007, 11:16 AM

Originally Posted by Shedhand

Wind Shear?

Windshear makes more of a "Humpty Dumpty" effect. And I bet the King's horses would still be crap at putting me back together again.

Greg

**jefferson** · 22nd July 2007, 06:40 PM

After all the feedback, I'm very reluctant to disclose too much about my latest stuff up. (Cut a bench top 12mm short, should have been 3m).

Nothing nasty out there, just some quiet chuckling from some.

All I can say is beware - the wood will eventually bite you! And then we'll all have long memories and chuckle loudly!

Jefferson

**Lignum** · 22nd July 2007, 06:43 PM

Originally Posted by jefferson

After all the feedback, I'm very reluctant to disclose too much about my latest stuff up. (Cut a bench top 12mm short, should have been 3m).

Jeff, i think you will need a very good gap filling glue

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