Replies

1. 
   Hastings | May 14, 2007 02:03am | #1

   Mortier:

   You should visit the Festool Owner's Group ( http://www.festoolownersgroup.com/ ) as you will see lots of completed projects. Rumor has it that Festool are comiing up with specific dominos for exterior work. But it is easy to make your own. I wouldn't use the standard beech dominos for exterior applications.

   Recently, there was quite a long post on the domino.

   Regards,

   Hastings

1. 
   MatthewSchenker | May 15, 2007 07:20pm | #10

   Yes, there has been extensive discussion at the Festool Owners Group regarding the Domino -- one of the hottest topics. The discussions have looked at basics of the machine, projects, and the latest strength test conducted by WOOD magazine.The project ideas speak for themselves: I've been very impressed at the variety of applications people have found for this tool.Regarding the WOOD magazine study, I'll have to wait until the magazine is published to examine it more closely, but the stats I've seen so far raise some questions. If you look at the photos Hastings posted, for example, you'll see that the wood cracked before the joint failed in the Domino, Dowelmax, and Beadlock system. The biscuit joint actually came apart. Again, I have not read the text of the review, but according to snippets I've read, the editors are deeming this a joint failure, which is highly suspect.There is also serious doubts that a dowel can be stronger than a loose tenon (that's what the Domino is).But final judgment should wait until the review is fully available.

   Edited 5/15/2007 12:22 pm ET by MatthewSchenker

1. 
   [email protected] | May 15, 2007 09:11pm | #11

   If the dowels are further apart than the loose tenon is wide, it is easily believed.

   The joints are being subjected to racking.  The wider the width of the connecting member, the longer lever arm it has to resist the load. 

   If the joint were subjected to a tension loading, the controlling factors would be the cross sectional area of the joining piece(s) whether they are a tenon, loose tenon, dowel, domino or biscuit, and the glue area.  A set of three dowels the same diameter as the thickness of the domino would have less cross sectional area, but more glue area.  Four dowels would have more cross sectional area, and more glue surface. 

1. 
   MatthewSchenker | May 21, 2007 05:37pm | #12

   I'm no expert on joint strength. However, long before the Domino was introduced I thought it was common wisdom that loose tenons are much stronger than dowels or biscuits.I thought it was also fairly well documented that if you are using an inferior joinery feature, like dowels or biscuits, that adding more of them does not increase strength.Based on this information, my question is, can two dowels, placed further apart, really be stronger than a loose tenon?My strong feeling is that there is no way dowels could beat the Domino. But the article is now available for everyone to review. It would be very interesting if people who know more about joinery could comment on the validity of WOOD's testing methodologies.

1. 
   [email protected] | May 21, 2007 06:40pm | #13

   It is all a matter of leverage, with a load that creates moment on the joint, then the load is carried by the extreme fiber, and the further it is to the far edge, the more th joint can carry. 

   In shear or pull out, it is a matter of surface area, and cross sectional area. 

   I'm not on my computer, or I would make a sketch that would illustrate what the mechanics are.  It is lots easier to understand if you can see a picture. 

2. 
   MatthewSchenker | May 21, 2007 08:51pm | #14

   Jigs-n-fixtures,
   On the shear strength, I think I see exactly what you mean. The surface area argument is the one I am accustomed to hearing.Regarding the load test, you wrote this:
   "It is all a matter of leverage, with a load that creates moment on the joint, then the load is carried by the extreme fiber, and the further it is to the far edge, the more th joint can carry."Are you referring to the depth of the joinery member? For example, does this mean that a biscuit may not be as strong as a dowel or a loose tenon because it may not extend as deep into the wood? Or do you mean that the closer a joinery member is to the surface (face) of the wood, the weaker the joint?

2. 
   pmmatty | May 14, 2007 03:24am | #2

   I have done extensive research on the domino and have ordered mine.  Was also involved in the post mentioned previously.  There is no question the dominos are stronger than biscuits.  They are loose tenons glued into mating mortises.  While there have been no strength tests performed that I am aware of, I expect them to be slightly weaker than traditional mortise and tenon.  PMM

1. 
   stantheman | May 14, 2007 03:33am | #3

   current issue of WOOD has strength test

1. 
   pmmatty | May 14, 2007 03:38am | #4

   how did the domino joint fare?  PMM

1. 
   stantheman | May 14, 2007 03:29pm | #5

   Had to go and rescue the magazine from recycle.  The article tested four "loose tenon" methods"  dowels (using Dowelemax), biscuits, domino and beadlock, vs regular M/T joint.  They were tested for shear strength, pull-apart stretngth, and speed of use.  M/T was strongest, as you would expect.  Surpisingly, dowels were second in both strength tests.  Domino were stronger than biscuits but biggest advantage was in speed, although biscuits were still faster.  The article recommended Domino as best overall choice (of the four) but the dowel as the lower cost alternative. 

1. 
   Hastings | May 14, 2007 03:53pm | #6

   Stan:Not surprisingly, there is quite a bit of chatter over on FOG about these tests. I have copied one particular post that shows the wood failing before the joint.Quote:The results posted by mr_hockey at the beginning of the thread were divided into two categories - Shear and Pull Apart. For ease of reference, the Pull Apart figures were:M&T 2525
   Dowel 1866
   Domino 1486
   Beadlock 1170
   bisquit [sic] 766My initial reaction was to assume that the the dowelled joint separated (pulled apart) at 1866, and the Dominoed joined separated at 1486, indicating that the dowelled joint could withstand 25% more pulling force than the Dominoed one, before the joint separated.bassman00 kindly found a video at http://www.woodmagazine.com/wood/story.jhtml?storyid=/templatedata/wood/story/data/1178129509968.xml which accompanies the testing article. It shows how each jointing system works, and although it doesn't show the testing in progress, it does show the failed joints, which are presumably those which were subjected to Pull Apart testing.I have taken the liberty of posting screenshots from three frames of that video, which show the failed joints. I have added labels to identify each joint:[see attached .jpg]Looking at how the joints have failed, it seems that only the biscuited joint has actually pulled apart. The Dominoed, Beadlocked and Dowelmaxed joints have remained intact, and the wood in the horizontal wooden member has split along its length, which stopped the test. Since it was the wood which seems to have failed in three cases, rather than the joint, I don't believe that the strength figures in the test can be reliably used to compare the strength of the three jointing methods. Instead, they primarily reflect the strength of the horizontal member. I say primarily, because we don't know how deep the various loose tenons were set into the horizontal member. If the end of any of the tenons extended beyond the split in the wood, then the part of the tenon beyond the split has indeed lost its grip in the surounding wood and failed (or the tenon has fractured).ForrestUnquoteHastings

   
2. 
   stantheman | May 14, 2007 07:02pm | #7

   Thanks for the interesting insights.  Just a hobbyist here, unlikely to buy either system, so I have no axe to grind.  I am just interested from an engineering standpoint.  It seems to me that the choice of joining method should be relevant to the intended use of the joint  In some cases wouldn't you want the joint to pull apart rather than break the wood under excessive load?  That is,  stength works against repairability?  

    

3. 
   Hastings | May 14, 2007 07:22pm | #8

   Stan:We had some Ethan Allen kitchen chairs (windsor) and they all fell apart within a year with normal wear and tear. We also have some antique Chippendale chairs in mahogany and most of the M&T joints have failed due in part to the glue drying out.It seems to me that joints rarely fail catastrophically when relatively new. What one wants to know is how well they stand up to the stresses of their intended use in their intended environment. While "raw" strength might be theoretically interesting, it's the constant minor stresses over time that really determine how a given joint will hold up.No one knows yet how the Domino will hold up (I would be willing to bet it will prove to be pretty good). This guy is using biscuits for some heavyduty work and they seem to hold up.http://www.woodworking.org/WC/GArchive98/Abstract/abstract1.htmlIntuitively, I would think the Domino would be stronger than biscuits.If you are making pieces to last for centuries, then it's hard to beat the traditional approaches.Hastings

4. 
   [email protected] | May 14, 2007 09:39pm | #9

   Actually, from an engineering standpoint, you want to do an initial design, analyze the design, and calculate the loads, and then size the components, and related joints to not fail under the expected loadings.   

   In reality, much of what is designed in woodworking is based on copying something that has stood the test of time, and using rules of thumb that have been developed over time. 

   For example, a tennon is supposed to be 1/3 the thickness of the thinner of the two pieces to be joined.  It works, and some day I intend to get the real strengths of woods I use from the "Wood As An Engineering Material" book, and actually figure out what it really should be.  And, I know going in that it will be close to 1/3. 

   Or, dovetails should be 1:6 in softwoods, and 1:7 or 1:8 in hardwoods depending on how hard the wood is.   I know that these angles work, and have stood the test of time.   And again, I fully intend to actually do an analyses based on the strengths of the materials I use, and figure out why. 

3. 
   cdesautels | May 10, 2020 01:08pm | #15

   I have the small Domino. (comes in two sizes). I love the thing and I find it's joints to be very strong. Or course a true mortise and tenon, properly cut, will be stronger, but I find the floating tenon the Domino uses is a very close second. I think it would do a fine job on a door if you doubled up the tenons. But if doors are your thing, I would recommend the larger version as it can take much larger tenons.

4. 
   geedubbee | May 10, 2020 01:49pm | #16

   I used floating tenons long before I got a Domino. I still do. Certainly you see people who use biscuits, or Dominos, or pocket screws for 'everything'. There are tablesaw and router books that show how to do anything under the sun with each tool; it slices, it dices ;-)

   As mentioned, your joining choice should be made for the case at hand. Mortise and tenon, bridle, half lap, dovetail, finger, the selection is wide and the uses are plentiful.