Author Topic: Domino Strength Test  (Read 23519 times)

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Offline Packard

  • Posts: 1692
Re: Domino Strength Test
« Reply #30 on: April 14, 2022, 11:43 AM »
I once made a face frame using half-lap joints. Instead of clamping, I used a single screw with a fender washer at each joint. 

Then I removed the screws.  What to do with the ugly hole in each joint?  I used my mortiser to cut square holes and I then pegged the joints. 

They were probably the world's strongest face frames.  I never did that again.  Too much work.  Now I use pocket holes as long as they don't show, otherwise, dowels.

I also did a full saddle joint on the drawer fronts.  (Not pegged, though.)

I am trying hard to not overbuild my projects.  I was proud that I was able to make a reasonable medicine cabinet using butt joints and a nail gun. [big grin] I was fairly amazed at how solid it felt. 

I may post a shot of that here. 

In my opinion, DowelMax makes the most outrageous strength claims.  It is almost as if they believe they invented the dowel joint. 

The key for validity of tests is "repeatability".  Since none of the online tests I have seen have been anything but a one-off, the repeatability is still a question. 

I did read a test run by the RTA (ready to assemble furniture association) where they tested various fasteners for (basically) sheet goods.  Dowels topped the crop.  It did better than screws (but not better than Confirmats).  It did better than dadoes, quarter-turn fasteners and those hidden nut fasteners. 

The kitchen cabinet association came up with similar results, with dowels topping the strength (again, mainly for sheet goods). 

They both concluded that the dowels should not be within 2" of the end of the joint. 

The kitchen cabinet test was less interested in racking strength because most of the cabinets used a wall as part of the structure. 

Surprisingly (to me) the dado joint did the most poorly of any joint tested.  I used to assemble cabinets using dadoes.  Now I dowel.  With the  right jig, is is just as fast and just as easy.






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Offline Cheese

  • Posts: 10180
Re: Domino Strength Test
« Reply #31 on: April 14, 2022, 12:24 PM »
I would like to test how clamping pressure effects lap joint strength though.

Along those lines I ran across this article and they mention that too much clamping pressure can actually squeeze the glue out of the joint.

https://www.woodmagazine.com/woodworking-tips/techniques/skills/take-it-easy-with-clamping-pressure










Offline ChuckS

  • Posts: 4013
Re: Domino Strength Test
« Reply #32 on: April 14, 2022, 03:04 PM »
I've never experienced glueline failure due to overclamping. As long as enough glue is applied to BOTH mating surfaces, I don't see how clamping can remove glue so much that it causes a starved joint.

Offline Packard

  • Posts: 1692
Re: Domino Strength Test
« Reply #33 on: April 14, 2022, 03:11 PM »
I can imagine it, but I have not experienced it.

I've bought "project boards" at Lowes.  This is some sort of "white wood", probably some species of pine.  The surface is a slick as a sheet of glass. 

I can imagine that almost no glue gets absorbed into the surface because of the slickness and lack of porosity. I have no documentation to support that, however.

I have not seen any real studies that support that either.  The "tests" we normally rely on in the woodworking field, are typically one step above anecdotal.  They are likely indicative of what they are testing, but not proof of those tests. 

There are really only manufacturers' associations that finance real testing, and those tests are specific to the types of construction used by the members.

The only really good tests that I have seen have been conducted by ready to assemble industry (think "Ikea") and the kitchen cabinet industry.  Both mostly interested in assembling particle board and plywood. 

Offline ChuckS

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Re: Domino Strength Test
« Reply #34 on: April 14, 2022, 07:05 PM »

Snip.
I can imagine that almost no glue gets absorbed into the surface because of the slickness and lack of porosity. I have no documentation to support that, however.
Snip.
I've not used any wood like that, but if almost no glue can get into the wood (pores), then even moderate clamping wouldn't help.

I've "overclamped" edge joints (panels) or butt joints (carcases) a lot, if not all the time, because of the clamps I use, and not one single joint has ever failed. The jaw clamps in my shop can exert well over 1,500 lb of force.

Despite my overclamping practice, by putting glue on BOTH mating surfaces, I've never had any joint failed on me in builds from chairs to tables to cabinets to frames, etc.

Putting glue on only one surface (which I've seen some do) is not something I feel comfortable with.
« Last Edit: April 14, 2022, 07:11 PM by ChuckS »

Offline Packard

  • Posts: 1692
Re: Domino Strength Test
« Reply #35 on: April 15, 2022, 08:44 AM »
I clamp until the glued joint closes up.  Sometimes that requires a lot of force,  in other instances very little.  My opinion is that a gap in the joint is worse than over-clamping.

But again, I have no studies to back that up.  It is just going on my feelings. 

In the last several years I have been using dowelled joints mostly.  The fit of the dowels really controls the amount of clamping pressure required.  Once the joint is "closed", I stop adding pressure.

Offline smorgasbord

  • Posts: 196
Re: Domino Strength Test
« Reply #36 on: September 06, 2022, 09:31 PM »
Yet another test of the strength of various joints:

Joint Test

Result still frame:


"That was a surprise. Based on this one test we should be building everything with dowels. But I want to emphasize this was an informal experiment."

I wonder what happens when two dominos are used (assuming the stock is wide enough).

Offline ChuckS

  • Posts: 4013
Re: Domino Strength Test
« Reply #37 on: September 06, 2022, 09:54 PM »
I've used double and twin dominoes in a table build in the form of a butt joint.

Fine Woodworking did a joinery test back in 2009:

« Last Edit: September 06, 2022, 09:58 PM by ChuckS »

Offline Packard

  • Posts: 1692
Re: Domino Strength Test
« Reply #38 on: September 07, 2022, 09:28 AM »
The problem with these seemingly “scientific” tests, is that they appear to test just one sample of each.

When I was in the metal stamping business, and we had to test parts for weld strength or hook strength, we always tested 10 or more pieces and recorded the values for each. There were sometimes outliers that tested higher or lower.  The ones that tested lower still had to remain within the strength tolerances. 

One sample makes good magazine or you tube fodder.  I don’t find it convincing.

On the other hand, various industries (think ready to assemble furniture—IKEA; and the kitchen cabinet trade association) do contract testing laboratories to test joinery.  Those results are based on multiple tests.

(It is the reason I changed from dado assembly of cabinets to dowels.  Dowels were vastly stronger, especially in racking strength.  Dominoes are not used by large cabinet companies as they cannot automate that process, so they are not included in the tests.)

Offline mino

  • Posts: 1210
Re: Domino Strength Test
« Reply #39 on: September 07, 2022, 10:32 AM »
It was already said, but I will add some more cruft that may help some hobbies:

TLDR ref. the "joint system strength" game:
IF one needs to ask "which joint system is stronger", one is asking the wrong question.

Instead, one shall go learn more about grain, about wood expand/contract, about glues chemistry, about mechanics etc. etc. When one will no longer see such a simplified (stupidified?) "test" as "enlightening", then one knows to have got the answers needed.


Some more mumblings of mine:
------------------------------------
The main advantages of the DOMINO system are:
 - easy/speed of use FOR AD HOC manufacturing /such flexibility is actually a detriment (!) in series production/
 - secondary function of ALIGNING the pieces /a non-issue in CNC-based mass manufacturing/
 - secondary function of ALLOWING EXACT FIT tuning /a detriment in CNC-based mass production/
 - flexibility, where one tool handles a WIDE RANGE OF APPLICATIONS /try joining 10 mm thick pieces with a 8mm dowel system .../

A dowel is:
 - cheap
 - not adjustable /a boon for mass manuf, a major issue for one-off custom work/
 - needs way more specialist machinery*) /basically a doweling machine/ to do time-cost-effectively

Of course a dowel configuration with no (time)cost spared will be better. Like 2x better. It will simple have more glue surface. That is why I use dowels with a doubled 32mm system for joints I need to have absolute maximum strength. But boy, are such joints expensive on mantime and overkill for 99% of cases.

To the contrary, the usual semi-dense DOMINO arrangement is about as strong as a /semi-dense/ dowel setup.


This means:
"Testing strength" between DOMINO/dowel/etc. is completely pointless:
 - if one needs maximum strength, cost be damned, then a well-balanced joint with both DOMINO and dowels will be stronger than the wood being joined
 - besides all the "tests" I saw so far were just scratching the surface and thei results were confusing at best and misleading at worst


DOMINO is the king of the hill on ad-hoc low volume custom production where it shines on time efficiency.
 - it is also very forgiving for free hand use

Dowels are the king of the hill on material cost which makes them ideal for series/mass production.
 - but are complete time disaster for one-off or ad-hoc work as need custom precision jigs etc.

DOMINO is the only /industrial/ game in town for narrow stock.
 - there are other options for 10-12 mm stock, but mostly manual work



*) DD40 excepted, that tool is a "Dowel DOMINO" in some ways, lacking the adjustability loose tenons provide
When The Machine has no brains, use yours.

Offline Coen

  • Posts: 1908
Re: Domino Strength Test
« Reply #40 on: September 07, 2022, 04:08 PM »
By the time you know it all, your life is up  [wink]

Offline Packard

  • Posts: 1692
Re: Domino Strength Test
« Reply #41 on: September 07, 2022, 04:11 PM »
Doweling is not necessarily slower than using a Domino. 

I have the CMT boring jig, a dowel jig made exclusively for work with sheet goods.  It is not very versatile, but it is very efficient with plywood, particle board or MDF. 

I do not have a Domino, but observing videos online I would suggest the following.

On narrow boards, where there is just one domino at the front and one at the rear and you are banking off the pins, the domino is faster.

On boards where a third domino is required in the middle, I would call the speed about even.

On wide boards, such as you might use for base cabinets, the CMT boring jig is faster. 

I am linking the IGM version, which is just the CMT boring jig with changed labels, because their videos are much better.  I got mine from Amazon.de (Germany), but the drill attachment is not currently available from them.  I use the drill attachment, but I also have a 14mm bushing for my plunge router and that will work also.

For cabinet work, which is mostly what I do, I like the dowels. 

I have a couple of other jigs for other applications, but the CMT gets most of the workout.

Note:  I have both the CMT boring jig and the CMT template.  The template is for when you need dowel holes in the middle of a sheet.  The jig is for edge to edge glue ups.

https://www.igmtools.com/category/woodworking-jigs/boring-dowel--hinges-jigs/
« Last Edit: September 07, 2022, 04:13 PM by Packard »

Offline smorgasbord

  • Posts: 196
Re: Domino Strength Test
« Reply #42 on: September 07, 2022, 04:44 PM »
Well, to be fair, Nick Engler himself said it wasn't a scientific test and that many more samples would have to be run.

Quote
a well-balanced joint with both DOMINO and dowels will be stronger than the wood being joined

Context matters here, too. First, if that were true, then the joints wouldn't have failed on the glue line, as they all did. Second, wood has two kinds of strength:
1) Strength along the grain
2) Strength against the grain

Glue adhesion also has various properties.  The "stronger than the wood being joined" really only applies to boards glued long grain to long grain, and that's because:
a) The glue adheres well on long grain
b) The wood is weakest across the grain.

You would never think to cantilever a piece of wood under load that has the grain running perpendicular to the cantilever, so even if you could get glue to adhere just as well to end grain as to long grain (and that's apparently doable), the joint would not be stronger than the wood in that direction.

It's worth pointing that dowels don't need any more specialized machines than dominos. To the contrary, you can successfully dowel with just a cheap dowel jig if you're careful and accurate. But, perhaps the real comparison is to the Mafell DD40 Duo Dowel System (they make at least two sizes there, too). About the same price and same ease of use as dominos (at least in the DF500 size). And it has the same cross-stops that eliminate measuring in many cases and ensure alignment.

Now, the domino system leaves you one degree of freedom for alignment mismatches whereas doweling doesn't. But, sometimes that's a disadantage, like when doing picture frame style miter joints. And dowels are much cheaper than dominos, and easier to shop-make, too.

In terms of strength, there have been enough different ad-hoc tests done that I am personally convinced that dowels can be stronger than dominos. What I suspect is going on is that a dowel is tight fitting all around while a domino is tight only on two faces, and the curve of the domino is actually wasted space in terms of contact area. For the test that Engler did in the video, the domino and (probably) manual mortise and tenon joint are relying on the glue to resist the initial movement. But, since the dowels fit tightly all around, they have some mechanical resistance as well. And, that could be the major difference/advantage.

So, one way to look at it is that the precision required for multiple dowels pays off in the added strength of the resulting joint, at least in some directions. Having the in-line with the domino alignment play (especially if you don't cut "tight" mortises) can be useful at times, but given our domino machine cross-stops it's not always (often?) necessary, and it does sacrifice some strength, IMO anyway.

A true square-cut, properly sized, M&T joint that fits tightly on all four surfaces is still going to be the strongest since it would combine the mechanical resistance in all directions with the highest glue surface area. But, cutting those where not just the cheeks fit tightly is really difficult.

I own a DF700 that I think is a great tool. But I am now wondering if, instead of buying the Seneca adapter and the DF500 domino/cutter set, I should have instead invested in the smaller Maffell doweler for those smaller size joints.

Offline Packard

  • Posts: 1692
Re: Domino Strength Test
« Reply #43 on: September 07, 2022, 05:23 PM »
One of the takeaways from the testing done by the kitchen cabinet manufacturers’ association was that no fastener should be within 2” of the end of a board.  Apparently, most sheet goods need surrounding material on both sides of a fastener or the plywood, particle board, or mdf will fail.

(They tested dowels, dry wall screws, confirmats, dadoes and 1/4 turn fasteners.  Surprisingly, racking tests the dadoes failed before they could get any reading at all, the 1/4 turn fasteners fared very poorly as did the dry wall screws. 

The confirmats excelled offering the racking strength of dowels with the ability to put the joint under tension.  They could be removed and re-installed several times without affecting performance. 

Of the joints with hidden fasteners, the dowels fared best.  If the joint was hidden, then confirmats did just as well (at a much higher cost).

Offline mino

  • Posts: 1210
Re: Domino Strength Test
« Reply #44 on: September 07, 2022, 09:34 PM »
...
It's worth pointing that dowels don't need any more specialized machines than dominos. To the contrary, you can successfully dowel with just a cheap dowel jig if you're careful and accurate.
...
And ... you just made my point here. It is not that it is not possible to use dowels. It is that their requirement for precision makes them expensive on time/total cost.

One cannot be accurate AND be time-effective at the same time with dowels. Not without specialised machinery or dedicated jigs for specific tasks. This works for series production, not so much for 2-3 pieces of a type.

I have some pretty high quality jig for doweling. It works well yet it is extremely limited on flexibility /compared to a DOMINO/ and the setup time (to be precise-enough) is just too much and the work itself is again, like 2x time.

Not counting my time, dowels are very cheap. Once I start counting my time, they are the most expensive thing. I still use them widely for extreme strength with some heavy-duty shop cabinets that I have a dedicated jig for. But that is about it.
When The Machine has no brains, use yours.

Offline luvmytoolz

  • Posts: 281
Re: Domino Strength Test
« Reply #45 on: September 07, 2022, 09:46 PM »
One thing worth mentioning is for sheet goods you can get the support bracket for the Domino to fit a rail guide, so it makes doing panels a no brainer.

Offline Mini Me

  • Posts: 343
Re: Domino Strength Test
« Reply #46 on: September 07, 2022, 10:26 PM »
Full disclosure, I own a Domino but I don't use it much for my own reasons and have never glued a domino into the mortise the machine creates because I see it as an alignment tool not a joint maker. From the first time I saw a Domino very shortly after they became available I thought it was a game changer for small scale industry where it saved time doing manual M&T joints and I am of the opinion that it was never aimed at the hobby workshop market and I still thing that way. Is there a long consistent number of complaints concerning Domino structural joints breaking and falling apart? the answer is no or I don't see them so I presume not so why is testing even needed?

Loose tenon joints have been around for a long time and it is not hard to make one either using a router or by hand and making the tenon is simplicity itself but for a professional making a living a Domino does that faster and more efficiently because the fiddling to final fit is taken away. I as a hobbyist do not work that way, time immersed in the hobby is not wasted time and I don't get concerned about how I spent it and if I did I wouldn't be doing it. I bought my Domino simply because it had been used to insert literally one Domino, put back in the box and never used again and was offered to me at an absurdly low price, my son uses it but for me as a hobbyist it is not something that fascinates me but if I was a small production shop I might own more than one.

Offline Packard

  • Posts: 1692
Re: Domino Strength Test
« Reply #47 on: September 07, 2022, 11:20 PM »
My understanding is that purchased dominoes, biscuits and fluted dowel are all compressed in manufacture and if you use a water based glue these items will all swell and make a tight fit.

In addition, fluted dowels can be further compressed by rolling them on a work surface using a piece of steel (I use a 12” metal working file for this.

While this can make multi dowel joints easier to assemble, my tests show that even these further compressed dowel swell up to make a tight fit.

My test was to briefly dip the dowels in water and insert the in an appropriate sized hole. The following day, aided by a vise grip pliers, I was able to pull them out, but only by twisting the in the hole first. At first they felt like they were glued in.

I only cut to length my own dowels when I want the cut ends to show for decorative effect.

Also, if you are making face frame cabinets where the cabinet sides do not show, then a couple of confirmats replace clamps and through dowels will do the trick and very quickly. If you are confident that you can drill perpendicular holes, then no dowel jig is needed.  Just draw a center line, drill add glue and tap in the dowels.  Alignment will always be perfect.

Offline smorgasbord

  • Posts: 196
Re: Domino Strength Test
« Reply #48 on: September 08, 2022, 02:00 AM »
...
It's worth pointing that dowels don't need any more specialized machines than dominos. To the contrary, you can successfully dowel with just a cheap dowel jig if you're careful and accurate.
...
And ... you just made my point here. It is not that it is not possible to use dowels. It is that their requirement for precision makes them expensive on time/total cost.

You left off the next sentence in my post, which is that real comparison is to the Mafell duo doweller. Let's compare like to like.  Both are about $1000 machines that make cutting their respective joints quick and easy. Complaining about making dowel joints with just a dowel jig is like complaining about making domino mortises with drill and drill jig. To do both quickly, you need the $1,000 machines.

And so, when you compare the two machines and the joints they're capable of, you get an interesting list of pros and cons for each. There is no clear winner for everyone. For small stock, you just can't get two dowels in (since they're spaced apart by a fixed amount), but you can get a domino in. For ultimate strength, however, the dowels go deeper (40mm each side, or 80 mm total) and provide mechanical locking in multiple directions instead of just one. For adjustability during glue-up, the domino gives you pretty good play along one axis, the doweler gives you none. And so on.

Offline luvmytoolz

  • Posts: 281
Re: Domino Strength Test
« Reply #49 on: September 08, 2022, 02:43 AM »
All I know is that if I could put a wig on my Domino It'd be sleeping beside me in bed!

I looove it! ;-)

I don't feel that way about my dowelling jig!
« Last Edit: September 08, 2022, 02:45 AM by luvmytoolz »

Offline Peter Parfitt

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Re: Domino Strength Test
« Reply #50 on: September 08, 2022, 03:48 AM »
Hi Everyone

We need to be careful not to over engineer our woodworking efforts. It is a different matter if the design requires high strength but for most purposes accurate cutting of stock and care with gluing will be enough to produce a great result.

To improve domino joint strength I would recommend that the narrow setting is used as this will improve shear strength which is important for joints where a load is expected at right angles to a component member.

Gluing and accurate stock preparation can have amazing results. The storage boxes that I made from very thin veneered MDF with no nails or dominos (just mitre joints and glue) have been in use for a very long time and both are used for about 3 kg of odds and ends:



Peter

Offline mino

  • Posts: 1210
Re: Domino Strength Test
« Reply #51 on: September 08, 2022, 05:40 AM »
You left off the next sentence in my post, which is that real comparison is to the Mafell duo doweller. Let's compare like to like.  Both are about $1000 machines that make cutting their respective joints quick and easy. Complaining about making dowel joints with just a dowel jig is like complaining about making domino mortises with drill and drill jig. To do both quickly, you need the $1,000 machines.

And so, when you compare the two machines and the joints they're capable of, you get an interesting list of pros and cons for each. There is no clear winner for everyone. For small stock, you just can't get two dowels in (since they're spaced apart by a fixed amount), but you can get a domino in. For ultimate strength, however, the dowels go deeper (40mm each side, or 80 mm total) and provide mechanical locking in multiple directions instead of just one. For adjustability during glue-up, the domino gives you pretty good play along one axis, the doweler gives you none. And so on.
Agreed. I explicitly put the DD40 aside in the original comment as DowelMax and such were the main topic ref dowels.
 [smile]

When I /and most people around/ think of dowel joints, I think of a "dowel line" arrangement. Be it on a 32mm grid or other. DD40 is a separate topic there. And sorry, $1000+ for DD40 is no "simple" or "cheap" by any sort of imagination. Yet it is still far, far, off from a doweling machine efficiency.

To me the best way to describe the DD40 is "A dowel DOMINO". That says it all.
When The Machine has no brains, use yours.

Offline Mini Me

  • Posts: 343
Re: Domino Strength Test
« Reply #52 on: September 08, 2022, 09:11 AM »
Hi Everyone

We need to be careful not to over engineer our woodworking efforts. It is a different matter if the design requires high strength but for most purposes accurate cutting of stock and care with gluing will be enough to produce a great result.

To improve domino joint strength I would recommend that the narrow setting is used as this will improve shear strength which is important for joints where a load is expected at right angles to a component member.

Gluing and accurate stock preparation can have amazing results. The storage boxes that I made from very thin veneered MDF with no nails or dominos (just mitre joints and glue) have been in use for a very long time and both are used for about 3 kg of odds and ends:

Peter

I agree with Peter's comments, I think dowells, dominos and biscuits are often used to overcome poor work and accuracy. Hobby WW's are mostly not pressed for time so why not do a good and accurate job in the first place and learn some basic joinery along the way.   

Offline HowardH

  • Posts: 1459
Re: Domino Strength Test
« Reply #53 on: November 19, 2022, 08:44 PM »
FW did a joinery test in 2008, including the dominoes: http://www.finewoodworking.com/2009/02/25/joint-strength-test

Part of the results:

DOWELMAX 759 lb.
¼ -IN. M&T 717 lb.
POCKET SCREW 698 lb.
DOMINO 597 lb.
BISCUIT 545 lb.

Kinda shocking that a Biscuit is essentially the same strength of a Domino. I would have never thought that.  My understanding is biscuits are really just for alignment and not strength. 
Howard H
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Offline mino

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Re: Domino Strength Test
« Reply #54 on: November 20, 2022, 08:50 PM »
FW did a joinery test in 2008, including the dominoes: http://www.finewoodworking.com/2009/02/25/joint-strength-test

Part of the results:

DOWELMAX 759 lb.
¼ -IN. M&T 717 lb.
POCKET SCREW 698 lb.
DOMINO 597 lb.
BISCUIT 545 lb.

Kinda shocking that a Biscuit is essentially the same strength of a Domino. I would have never thought that.  My understanding is biscuits are really just for alignment and not strength.
That "test" is more misleading than useful.

For a proper representative test one would need:
 - 4+ samples per test
 - test multiple angles of applied force (say 0˚, 15˚, ...)
 - "durability test", i.e. having it repeatedly face an otherwise non-breaking force
 - repeat the test after some time
 - repeat the test after a couple wet/dry cycles
 - couple more which I did not think of now

In other words. EVERY single of those connection methods can be made to "win" as long as one chooses the "right" test method ... what was it that Mr. Churchil said about statistics ?

 [smile]
When The Machine has no brains, use yours.

Offline ChuckS

  • Posts: 4013
Re: Domino Strength Test
« Reply #55 on: November 20, 2022, 09:02 PM »
Did you read the whole article? The article has included some caveats to avoid people accusing it of being misleading. The article isn't about any particular winning joint as the winning criterion is not necessarily the strength (if it were, I'd be building everything with pocket screws instead of dominoes). The article is more about the relative joint strengths in the conditions set out for the test.
« Last Edit: November 21, 2022, 12:37 AM by ChuckS »

Offline Svar

  • Posts: 2515
Re: Domino Strength Test
« Reply #56 on: November 21, 2022, 01:48 AM »
For a proper representative test one would need:
 - 4+ samples per test
 - test multiple angles of applied force (say 0˚, 15˚, ...)
 - "durability test", i.e. having it repeatedly face an otherwise non-breaking force
 - repeat the test after some time
 - repeat the test after a couple wet/dry cycles
 - couple more which I did not think of now
FW did make multiple (>4) replications of each joint as described. Having said that, in some cases 3 may suffice, in others 20 is not enough. Dealing with wood, I'd err on the greater number.
Multiple angles would yield the same result, just scaled. But shear stress test might not.
The article is useful, as it clearly says what was tested and what was not. No experiment tests everything. Frankly nothing surprising there. This is roughly how I would rate those joints if I had to guess.
A full 1/2 thickness spline they suggested (but did not test) on page 38 lower right corner, would have been by far the best.

what was it that Mr. Churchil said about statistics ?
He and his predecessor, who had even more radical opinion, knew little about actual statistics. I typically ignore amateurish "bumper sticker wisdom".
« Last Edit: November 21, 2022, 01:53 AM by Svar »

Offline ChuckS

  • Posts: 4013
Re: Domino Strength Test
« Reply #57 on: November 21, 2022, 08:52 AM »
I should add that someone did a similar joinery experiment, and that was shared and discussed in this forum not too long ago. The results were similar to those published by FW 14 years ago.

P.S. Here is one of the many joinery tests out there. I didn't watch this one, but found a summary result shared in one of the comments.

https://m.youtube.com/watch?v=CE147Ow7RmM&feature=youtu.be



« Last Edit: November 21, 2022, 10:06 AM by ChuckS »

Offline HowardH

  • Posts: 1459
Re: Domino Strength Test
« Reply #58 on: November 21, 2022, 12:33 PM »
For a proper representative test one would need:
 - 4+ samples per test
 - test multiple angles of applied force (say 0˚, 15˚, ...)
 - "durability test", i.e. having it repeatedly face an otherwise non-breaking force
 - repeat the test after some time
 - repeat the test after a couple wet/dry cycles
 - couple more which I did not think of now
FW did make multiple (>4) replications of each joint as described. Having said that, in some cases 3 may suffice, in others 20 is not enough. Dealing with wood, I'd err on the greater number.
Multiple angles would yield the same result, just scaled. But shear stress test might not.
The article is useful, as it clearly says what was tested and what was not. No experiment tests everything. Frankly nothing surprising there. This is roughly how I would rate those joints if I had to guess.
A full 1/2 thickness spline they suggested (but did not test) on page 38 lower right corner, would have been by far the best.

what was it that Mr. Churchil said about statistics ?
He and his predecessor, who had even more radical opinion, knew little about actual statistics. I typically ignore amateurish "bumper sticker wisdom".

I actually like what Mark Twain said about statistics: "There are three kinds of lies: lies, damned lies and statistics."  :)
Howard H
The Dallas Texas Festool Fanatic!

Mark Twain:  "I didn't attend the funeral, but I sent a letter approving of it." "If you tell the truth you don't have to remember anything."

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