Michael Kellough
Member
Mike_Chrest said:
I'd like to know how this joint would fare with the load applied in the opposite direction.
Strength of Domino... Test Results
- Thread starter mr_hockey
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I'd like to know how this joint would fare with the load applied in the opposite direction.
Michael Kellough said:
Yes, I'm quite aware of the brilliant application of the dominoes hence the "should want to separate easily" statement. In fact, I received the Woodcraft Mag before I saw his post about that chair and was thrilled to see he now posts here.
One question I've always wondered about is if you made integral tenons the same size as dominoes or loose tenons or even dowels, wouldn't they all perform the same? And since the wood failed, isn't more a result of the wrong species of wood being used? Also, wouldn't a table have more than one right angle joint that combine to create a sturdier structure? Finally, am I asking too many questions?
PaulD
bassman00 said:One question I've always wondered about is if you made integral tenons the same size as dominoes or loose tenons or even dowels, wouldn't they all perform the same? And since the wood failed, isn't more a result of the wrong species of wood being used? Also, wouldn't a table have more than one right angle joint that combine to create a sturdier structure? Finally, am I asking too many questions?
PaulD
Paul, YES, NO, NO, YES (but not necessarily in that order)! Sorry, couldn't resist. LOL
Dave
Mike_Chrest
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Michael,
I'd like to know how this joint would fare with the load applied in the opposite direction.
I think it would act like the T shaped samples in the Torture Test article. It would be a lot harder to split. I have to come up with a more accurate force measurement system, then I'll break some more joints.
Paul D.,
if you made integral tenons the same size as dominoes or loose tenons or even dowels, wouldn't they all perform the same?
Since the mortise part of the joint is the weak element, loose tenons act the same as integral tenons. Thats why I found the first Torture test article so interesting. He studied wider tenons VS deeper tenons and found wider tenons stronger. The Domino can make wider tenons easily. It can't do deeper tenons. He didn't study thicker tenons( he used 1/3 thickness rule).
I think he used one 8mm x 50mm Domino for the second article and compaired that to the 1/4" thick integral tenons which are stronger in 3/4" material.
since the wood failed, isn't more a result of the wrong species of wood being used
The wood at the back of the mortise always fails. Poplar M&T joints will be weaker than oak M&T joints. But, by changing the proportions of the joint you can more than double the strength for the given species. I use a lot of poplar in my work so that is what I wanted to study.
Also, wouldn't a table have more than one right angle joint that combine to create a sturdier structure
Yes, ideally the stress is spread out to all four legs of the table as well as any spreaders. It would be a worse case scenario to snag one leg.
I'd like to know how this joint would fare with the load applied in the opposite direction.
I think it would act like the T shaped samples in the Torture Test article. It would be a lot harder to split. I have to come up with a more accurate force measurement system, then I'll break some more joints.
Paul D.,
if you made integral tenons the same size as dominoes or loose tenons or even dowels, wouldn't they all perform the same?
Since the mortise part of the joint is the weak element, loose tenons act the same as integral tenons. Thats why I found the first Torture test article so interesting. He studied wider tenons VS deeper tenons and found wider tenons stronger. The Domino can make wider tenons easily. It can't do deeper tenons. He didn't study thicker tenons( he used 1/3 thickness rule).
I think he used one 8mm x 50mm Domino for the second article and compaired that to the 1/4" thick integral tenons which are stronger in 3/4" material.
since the wood failed, isn't more a result of the wrong species of wood being used
The wood at the back of the mortise always fails. Poplar M&T joints will be weaker than oak M&T joints. But, by changing the proportions of the joint you can more than double the strength for the given species. I use a lot of poplar in my work so that is what I wanted to study.
Also, wouldn't a table have more than one right angle joint that combine to create a sturdier structure
Yes, ideally the stress is spread out to all four legs of the table as well as any spreaders. It would be a worse case scenario to snag one leg.
Mike,
Have you done any more testing?
To summarize what I could find in this post, you ran three joints:
(2) 8mm(x50?) tenons failed at 100 ft-lbs
(1) 8mm(x50?) tenon failed at 200 ft-lbs (awesome data point - inverse linear relationship between volume of mortises and strength of joint)
(2) 6mm (x40) tenon did not fail at 200 ft-lbs (there goes our linear relationship...)
Questions raised: what about (1) 5mm tenon? (2) 5mm tenons? Difference between 8x40 and 8x50 in single and double config?
It seems to me that our intuitions are the opposite of reality on these joints. My intuition is the tenon is so small compared to the size of the joint, that we need more tenon: longer, thicker, wider. But it looks like with modern glue and beech tenons that the weakest link is the wood around the mortise. So it would be very interesting if we could find the point at which the glue fails at the tenon - this might give us an idea of the minimum required mortise size.
More rambling - when we create the mortise, we weaken the wood. We have not seen any tenon failures yet, so maybe we are weakening the wood more than necessary. By finding the point at which the actual glue joint fails, we can find the minimum required mortise.
I also wonder about the results over time. With cross grain expansion and contraction, will the rail to stile joint (the part that has no domino) fail first because the width is greater across the whole joint then just across the domino? At that point, would the strength of the joint be more related to the glue area of the mortise and tenon, at which point more tenon(quantity, thickness, length, width) may be stronger? Perhaps a test could be done where glue is only applied to the domino and not to the actual rail to stile contact.
Another crazy thought, if the wood is failing by splitting at the base of the mortise, maybe vertical grain stiles would be weaker than flat grain stiles?
I am currently building a furniture grade fence with no fasteners (other than glue) out of Clear Western Red Cedar - a soft wood. I suspect that these effects will be even more pronounced as the strength of the wood decreases. I was using loose tenons - about 4" long Baltic Birch plywood tenons. I now have a Domino, so I am trying to maximize the strength with loose tenons that are less than half the size.
I may do some tests of my own on some cedar samples, has your testing rig evolved at all? Do you think a force gauge(like a hanging weight scale for weighing livestock or game) connected to a ratcheting tie down would work?
Thanks,
Randy
Have you done any more testing?
To summarize what I could find in this post, you ran three joints:
(2) 8mm(x50?) tenons failed at 100 ft-lbs
(1) 8mm(x50?) tenon failed at 200 ft-lbs (awesome data point - inverse linear relationship between volume of mortises and strength of joint)
(2) 6mm (x40) tenon did not fail at 200 ft-lbs (there goes our linear relationship...)
Questions raised: what about (1) 5mm tenon? (2) 5mm tenons? Difference between 8x40 and 8x50 in single and double config?
It seems to me that our intuitions are the opposite of reality on these joints. My intuition is the tenon is so small compared to the size of the joint, that we need more tenon: longer, thicker, wider. But it looks like with modern glue and beech tenons that the weakest link is the wood around the mortise. So it would be very interesting if we could find the point at which the glue fails at the tenon - this might give us an idea of the minimum required mortise size.
More rambling - when we create the mortise, we weaken the wood. We have not seen any tenon failures yet, so maybe we are weakening the wood more than necessary. By finding the point at which the actual glue joint fails, we can find the minimum required mortise.
I also wonder about the results over time. With cross grain expansion and contraction, will the rail to stile joint (the part that has no domino) fail first because the width is greater across the whole joint then just across the domino? At that point, would the strength of the joint be more related to the glue area of the mortise and tenon, at which point more tenon(quantity, thickness, length, width) may be stronger? Perhaps a test could be done where glue is only applied to the domino and not to the actual rail to stile contact.
Another crazy thought, if the wood is failing by splitting at the base of the mortise, maybe vertical grain stiles would be weaker than flat grain stiles?
I am currently building a furniture grade fence with no fasteners (other than glue) out of Clear Western Red Cedar - a soft wood. I suspect that these effects will be even more pronounced as the strength of the wood decreases. I was using loose tenons - about 4" long Baltic Birch plywood tenons. I now have a Domino, so I am trying to maximize the strength with loose tenons that are less than half the size.
I may do some tests of my own on some cedar samples, has your testing rig evolved at all? Do you think a force gauge(like a hanging weight scale for weighing livestock or game) connected to a ratcheting tie down would work?
Thanks,
Randy
I had somehow missed this thread, thanks for bumping it Randy.
It's funny, but the first thing I thought when I read everything was, "why don't they add functionality to the next generation of Domino so you can lock out the pendulum action?". Granted you'd be left with a drill, albeit a very accurate one. Your choice of possible joint options would be increased to two, unless you live in Humboldt county or Amsterdam. Ze Chermans probably wouldn't even consider it because they wouldn't sell as many consumables, not to mention they've already determined the best joining option and don't give a Rat's a** what anybody else thinks.
It's funny, but the first thing I thought when I read everything was, "why don't they add functionality to the next generation of Domino so you can lock out the pendulum action?". Granted you'd be left with a drill, albeit a very accurate one. Your choice of possible joint options would be increased to two, unless you live in Humboldt county or Amsterdam. Ze Chermans probably wouldn't even consider it because they wouldn't sell as many consumables, not to mention they've already determined the best joining option and don't give a Rat's a** what anybody else thinks.
Mike_Chrest
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Randy,
I haven't gotten around to the new testing yet. I have been using the Domino a lot(last project had 630 Domino's in it, thats 1260 holes).
The ratchet and scale should work, but you have to watch the scale to tell how much force was applied when the wood breaks( it happens real quick).
With weights you know how much force you applied even after the excitement of broken stuff flying around. Also spring scales are not as consistant as gravity.
You can get some design ideas from the articles in Wood magazine( you can download them for a small fee if you don't want to hunt up the back issues).
From what I saw the tennon is the strongest part of the joint. The part of the joint where the loose tennon is glued into the rail never broke. The wood breaks at the back of the mortise in the style where there is a small pocket for extra glue(the tennon is not reinforcing the sides of the mortise here).
For your cedar fence you might consider plunging the Domino from both sides of the style and making some extra long tennon stock from cedar.
Since we first started this thread Fine Woodworking did another glue test article with much better testing than they did a few years ago.
Mike
I haven't gotten around to the new testing yet. I have been using the Domino a lot(last project had 630 Domino's in it, thats 1260 holes).
The ratchet and scale should work, but you have to watch the scale to tell how much force was applied when the wood breaks( it happens real quick).
With weights you know how much force you applied even after the excitement of broken stuff flying around. Also spring scales are not as consistant as gravity.
You can get some design ideas from the articles in Wood magazine( you can download them for a small fee if you don't want to hunt up the back issues).
From what I saw the tennon is the strongest part of the joint. The part of the joint where the loose tennon is glued into the rail never broke. The wood breaks at the back of the mortise in the style where there is a small pocket for extra glue(the tennon is not reinforcing the sides of the mortise here).
For your cedar fence you might consider plunging the Domino from both sides of the style and making some extra long tennon stock from cedar.
Since we first started this thread Fine Woodworking did another glue test article with much better testing than they did a few years ago.
Mike
Matthew Schenker
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Mike Chrest said:Randy,
I haven't gotten around to the new testing yet. I have been using the Domino a lot(last project had 630 Domino's in it, thats 1260 holes).
Sorry for the delays, but have you posted photos of this project? That's a lot of Dominos! And since you were a Domino raffle winner, you have a steep responsibility here (Domino Raffle Winners). Where's Dan when we need him to be policing members?
Mike Chrest said:
More photos! This would be a great thing to document. As you mentioned, Fine Woodworking did a glue test recently. But what would be really helpful is specific information about various Domino joints, with photos and descriptions of various Domino joints tested by FOG members. Remember, people who are thinking of buying the Domino want to know how easy it is to use, and how strong the joints are.
I'm thinking of doing some tests myself. But maybe we could organize this a bit? What specific types of tests do people want to see? If we had a rough list of questions people have about Domino strength, those of us who have the tool could then set out to illustrate the answers.
What do you think?
Matthew
Jerry Work
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Hi Mathew,
Ease of use and joint strength are but two of the many virtues of the Domino. I personally think too much attention goes the the strength issue as any M&T joint is much stronger than other joinery techniques anyway, and is usually far stronger than the surrounding wood itself. If one is worried about joint strength, simply add another loose tenon or two to the joint (within reason). For day in day out custom furniture making I find the Domino's greatest value is in precisely positioning two pieces of wood realative to one another. Rail, stile and panel components go together square, aligned and strong by simply adding a Domino to the inside of the tongue and grove where a rail and stile mate. This Domino prevents the rail from sliding in the grove on the stile during clamping so the assembly remains properly aligned at this critical and usually very visable joint. If you wait to cut the Domino mortise until after you have profiled the rail and stile (as I normally do), then the alignment pins on the Domino have no purchase since they will often fall in the grove on the stile piece. That is where the triangle cut outs on the fence come in so handy. You can look throught this triangle and align the point of the triangle with the end of the stile by eye since the point of the triangle is even with the edge of the alignment pin. Same with the scribe lines on the clear plastic portion of the fence. These can be aligned with the ends and edges of two components to properly align them without ever measuring or marking anything. If you cut the Domino mortise after cutting the tongue on center stiles, the tongue remaining after groving both sides of this component can become narrow enough that it will fall inside the machined area on the front of the Domino machine where the bit exits. It is simple enough to use the saddle fence to center the Domino cutter on the end of this center stile and by eye keep the end of the tongue aligned with the face of the Domino machine. Again, no marking or measuring is required. Another great trait of the Domino is that the tenons do not swell up the way biscuits do so on thin weak panels (like the 10mm thick book matched burl sets I commonly use) you won't see the tell tale biscuit shape when light plays off of the face of the glued up panel. I did a bit of judicious filing on my fence so it will go down to within 5mm of the center line of the work piece so I can use 5mm Dominos to edge join these 10mm thick panels. Finally, using Dominos with or without glue to align two pieces of wood really simplifies any number of wood movement design issues that are not easy to tackle any other way. So, ease of use and strength are important Domino attributes, but are far from the most important from my POV. I, for one, think these other uses are of far more impact for most furniture makers than all the focus on joint strength and would like to see the discussion move in these directions instead. Hope this helps.
Jerry
Ease of use and joint strength are but two of the many virtues of the Domino. I personally think too much attention goes the the strength issue as any M&T joint is much stronger than other joinery techniques anyway, and is usually far stronger than the surrounding wood itself. If one is worried about joint strength, simply add another loose tenon or two to the joint (within reason). For day in day out custom furniture making I find the Domino's greatest value is in precisely positioning two pieces of wood realative to one another. Rail, stile and panel components go together square, aligned and strong by simply adding a Domino to the inside of the tongue and grove where a rail and stile mate. This Domino prevents the rail from sliding in the grove on the stile during clamping so the assembly remains properly aligned at this critical and usually very visable joint. If you wait to cut the Domino mortise until after you have profiled the rail and stile (as I normally do), then the alignment pins on the Domino have no purchase since they will often fall in the grove on the stile piece. That is where the triangle cut outs on the fence come in so handy. You can look throught this triangle and align the point of the triangle with the end of the stile by eye since the point of the triangle is even with the edge of the alignment pin. Same with the scribe lines on the clear plastic portion of the fence. These can be aligned with the ends and edges of two components to properly align them without ever measuring or marking anything. If you cut the Domino mortise after cutting the tongue on center stiles, the tongue remaining after groving both sides of this component can become narrow enough that it will fall inside the machined area on the front of the Domino machine where the bit exits. It is simple enough to use the saddle fence to center the Domino cutter on the end of this center stile and by eye keep the end of the tongue aligned with the face of the Domino machine. Again, no marking or measuring is required. Another great trait of the Domino is that the tenons do not swell up the way biscuits do so on thin weak panels (like the 10mm thick book matched burl sets I commonly use) you won't see the tell tale biscuit shape when light plays off of the face of the glued up panel. I did a bit of judicious filing on my fence so it will go down to within 5mm of the center line of the work piece so I can use 5mm Dominos to edge join these 10mm thick panels. Finally, using Dominos with or without glue to align two pieces of wood really simplifies any number of wood movement design issues that are not easy to tackle any other way. So, ease of use and strength are important Domino attributes, but are far from the most important from my POV. I, for one, think these other uses are of far more impact for most furniture makers than all the focus on joint strength and would like to see the discussion move in these directions instead. Hope this helps.
Jerry
Matthew Schenker said:Mike Chrest said:Randy,
I haven't gotten around to the new testing yet. I have been using the Domino a lot(last project had 630 Domino's in it, thats 1260 holes).
Sorry for the delays, but have you posted photos of this project? That's a lot of Dominos! And since you were a Domino raffle winner, you have a steep responsibility here (Domino Raffle Winners). Where's Dan when we need him to be policing members?
Mike Chrest said:
More photos! This would be a great thing to document. As you mentioned, Fine Woodworking did a glue test recently. But what would be really helpful is specific information about various Domino joints, with photos and descriptions of various Domino joints tested by FOG members. Remember, people who are thinking of buying the Domino want to know how easy it is to use, and how strong the joints are.
I'm thinking of doing some tests myself. But maybe we could organize this a bit? What specific types of tests do people want to see? If we had a rough list of questions people have about Domino strength, those of us who have the tool could then set out to illustrate the answers.
What do you think?
Matthew
I have to agree with Jerry on this point. Since the motice and tenon joint, loose tenon or otherwise, is inherently stronger than other joinery extensive glue tests just tend to perpetuate the notion that there is some inherent weakness in Domino joinery. At the end of the day you will still have a bunch of joints that fail at the bottom of the mortice. We already know that is going to happen and it is a function of the strength of the wood. In essence you are testing the wood and not the joint. Jerry has it right. Strength needs to be addressed in the design of the piece. The M&T joint gives you a leg up over other joints in that regard already and the Domino gives you a way to use that joint quickly and accurately, the very things that were the limiting factors in M&T use previously.
Matthew Schenker
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Jerry Work said:
I agree with you, and I have learned to trust the Domino joint's strength. But my point is that new customers want to know these things, and do question the basics. I think a way to assure people about joint strength and/or ease of use is to illustrate it.
Of course, as many forum discussions have shown, there are many more interesting questions about the Domino!
Matthew
Mike_Chrest
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Hi Matt,
Yes,I have posted pictures, but I get no comments ??? Maybe members (and administrators ;D) don't look in the projects section? Or my project looks like crap? Any way, I will try to make some time to break some more wood. Here is what Pocket screws look like after exploding.[attachthumb=#]
Mike
Yes,I have posted pictures, but I get no comments ??? Maybe members (and administrators ;D) don't look in the projects section? Or my project looks like crap? Any way, I will try to make some time to break some more wood. Here is what Pocket screws look like after exploding.[attachthumb=#]
Mike
Mike_Chrest
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Jerry,
I don't think you read this whole thread. When I broke samples I found that one 8mm Domino was stronger than two 8mm Dominos in 3/4" poplar stock. That was what surprised me and got me interested in testing the joints.
Mike
I don't think you read this whole thread. When I broke samples I found that one 8mm Domino was stronger than two 8mm Dominos in 3/4" poplar stock. That was what surprised me and got me interested in testing the joints.
Mike
Dixon Peer
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All this "scientific" testing of joinery is interesting, for sure, but most of what we do doesn't need more strength than the Domino can deliver. If you're building rocking chairs, or any kind of chair (people tend to rock back in a chair even though it's not a rocker), you need all the strength you can get. Then you go for the traditional mortise and tenon joint. But for cabinet face frames and such, these tests mean very little.
Mike_Chrest
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Dixon,
This is true. The reason I got so interested in the joint strength issue was that I was offered a commission to build a bunch of meditation platforms. While this may sound like it doesn't require much design for strength, consider that 50 people will sit on them and groups of 15 to 20 will jump up from a seated posture, spring off and run to interview with the Zen teacher (20 x 170lbs=3400lbs)
Mike
Oh, and the inner layer is poplar!
This is true. The reason I got so interested in the joint strength issue was that I was offered a commission to build a bunch of meditation platforms. While this may sound like it doesn't require much design for strength, consider that 50 people will sit on them and groups of 15 to 20 will jump up from a seated posture, spring off and run to interview with the Zen teacher (20 x 170lbs=3400lbs
)Mike
Oh, and the inner layer is poplar!
Matthew Schenker
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Mike Chrest said:
I do check the projects section. Unfortunately, I didn't make the connection between that project and your comments here in this discussion. Now I see the connection! Sorry about that.
I assume you're referring to this project ---> louver ceiling project
Maybe now more people will respond!
Matthew
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Matthew Schenker said:
Dave Ronyak
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Mike Chrest said:Dixon,
This is true. The reason I got so interested in the joint strength issue was that I was offered a commission to build a bunch of meditation platforms. While this may sound like it doesn't require much design for strength, consider that 50 people will sit on them and groups of 15 to 20 will jump up from a seated posture, spring off and run to interview with the Zen teacher (20 x 170lbs=3400lbs
Mike
Oh, and the inner layer is poplar!
And when they jump, the local load could rise to as much as 4X the static load.
Dave R.
Mike_Chrest
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Well they haven't collapsed yet :
The platforms are a holdover from Japan where the monks sleep in the meditation hall and store their bedding under the platforms(called tans). The retreat center has dorms so mostly extra cushions get stored under there.
[attachthumb=#]
There is a whole box of Domino's holding these people up. How's that for a stress test? When I get done with exterior trim I have to face these with 3/4" cherry so they will be twice as strong. The plywood top gets covered with tatami (rice straw)mat.
The platforms are a holdover from Japan where the monks sleep in the meditation hall and store their bedding under the platforms(called tans). The retreat center has dorms so mostly extra cushions get stored under there.[attachthumb=#]
There is a whole box of Domino's holding these people up. How's that for a stress test? When I get done with exterior trim I have to face these with 3/4" cherry so they will be twice as strong. The plywood top gets covered with tatami (rice straw)mat.