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Floating tenons - pros and cons

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  • Floating tenons - pros and cons

    On my latest project I messed up when cutting my rails and did not leave the extra length required for the tenons on the ends. Not wanting to waste the wood, I decided to use floating tenons instead. What struck me was how much simpler it was. I did not have to learn or perform two skills (make clean mortices and correctly fitting tenons). I really only had to make nice clean mortices. Making the floating tenon stock was simple. Also, due to setup tolerances I often have issues with one shoulder of a tenon being offset from the other just by a hair. This would have to be tweaked using a shoulder plane or something. Using floating tenons you just need cut the board square to the length you want between the stiles. Making tenons is a multi-step process potentially using more than one tool. Making floating tenons is as simple as planing wood to a certain thickness and cutting to size.

    So, having said all of that, what are the downsides? Is there really any meaningful difference in joint strength between the two methods, especially as it relates to furniture projects?

    What say you all?
    nnieman likes this.
    Cheers
    Randy
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  • #2

    Re: Floating tenons - pros and cons

    If you're in the camp that believes the glue line itself is stronger than the wood, then there's nothing to suggest that a floating tenon isn't as strong as an integral tenon. Glues of today are widely believed to be much stronger than the glues of yesteryear.

    This is part of the reason why dominoes are so well adopted in today's woodworking. They are just as strong as the same sized integral tenon, and a helluva lot quicker.

    I can't think of any downsides at all. In furniture making, I do integral tenons just cause I do integral tenons. I can see that in other building types where glue is not used, like timber framing or other types of interlocking (dry) joinery, then they might not be as easy to use.

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    • #3

      Re: Floating tenons - pros and cons

      Originally posted by Scott Walsh View Post
      If you're in the camp that believes the glue line itself is stronger than the wood, then there's nothing to suggest that a floating tenon isn't as strong as an integral tenon.
      That's true for a tenon glued into a cross grain mortise, but not necessarily so for a loose tenon stuck into a long grain part, especially if it's a short tenon. The end of the loose tenon has no bond with the end grain at the bottom of its mortise. With a short loose tenon, it will be relying only on the bond between the sides of the tenon & the mortise. I don't know at what depth the broken end grain is no longer a factor.

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      • #4

        Re: Floating tenons - pros and cons

        One issue might be chopping a mortise in end grain and having a high(er?) potential of splitting the board? I suppose drilling the mortise would alleviate that issue.

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        • #5

          Re: Floating tenons - pros and cons

          Originally posted by drzaius View Post

          That's true for a tenon glued into a cross grain mortise, but not necessarily so for a loose tenon stuck into a long grain part, especially if it's a short tenon. The end of the loose tenon has no bond with the end grain at the bottom of its mortise. With a short loose tenon, it will be relying only on the bond between the sides of the tenon & the mortise. I don't know at what depth the broken end grain is no longer a factor.
          I see what you're saying. I'd be interested in seeing this tested.

          For the purpose of furniture making, I believe that the strength of a loose tenon would be more than adequate.

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          • #6

            Re: Floating tenons - pros and cons

            I don't think there's any issue with a floating tenant. I don't know if it's stronger long term...

            I like the challenge of making a perfect mortise and tenon joint. I find it enjoyable. Not saying for production runs I would totally use them. If I am building a quality piece that I am charging top dollar then I don't mind going the extra little bit and doing it the old fashion way... Which includes pinning joints

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            • #7

              Re: Floating tenons - pros and cons

              I have repaired a few chairs recently, both old and newish, all with dowel joints, yes I know its a dowel not a domino, the old chairs were glued up with animal glue and we know how that shrinks and lets go the dowels were hand made not round and those chairs were old.
              The new chairs, were made to look at and not to use, the hole was drilled deeper than the dowel went in so an empty hole was a weak point, the dowels had broke, a domino had 3 & 4 times the strength, there was so little wood left in some cases after the dowel hole was drilled it was weak to start with and the legs were only fixed at the top no rail, and people lean back on the back legs, abuse.
              What I am trying to say here is mostly we see the faults and weak points of our construction only when it fails, when something is holding together well we don't look and say "that's a good joint".
              I started making wooden windows and doors in 1968 using mortise and tenon joints in those days we would haunch the joint this was a practice developed because the glues of the day were not good enough now with our glues being what they are a haunch is unnecessary IMHO, I have seen the effects of weather on mortise and tenon joints too and if the maintenance is lacking or there is abuse a mortise and tenon will break.
              All just my observations, probably worth what you paid for it.

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              • #8

                Re: Floating tenons - pros and cons

                Question. My understanding was a dowel or floating tenon should have a bit of space at the bottom of the hole for glue. This allows ease of entry and prevents hydraulic lock producing a joint that won't close. A couple of post here seem to indicate there should be contact at the bottom if I am reading them correctly. What is the general feeling on this?
                To answer the original question - I have used dowels and floating tenons for years with success.
                Redneck Albertan likes this.

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                • #9

                  Re: Floating tenons - pros and cons

                  Originally posted by dwoody View Post
                  Question. My understanding was a dowel or floating tenon should have a bit of space at the bottom of the hole for glue. This allows ease of entry and prevents hydraulic lock producing a joint that won't close. A couple of post here seem to indicate there should be contact at the bottom if I am reading them correctly. What is the general feeling on this?
                  To answer the original question - I have used dowels and floating tenons for years with success.
                  There has to be a small gap at the bottom IMO.
                  Cheers
                  Randy

                  Comment


                  • #10

                    Re: Floating tenons - pros and cons

                    Originally posted by dwoody View Post
                    Question. My understanding was a dowel or floating tenon should have a bit of space at the bottom of the hole for glue. This allows ease of entry and prevents hydraulic lock producing a joint that won't close. A couple of post here seem to indicate there should be contact at the bottom if I am reading them correctly. What is the general feeling on this?
                    To answer the original question - I have used dowels and floating tenons for years with success.
                    Yes a small gap 2mm 1/8" the chairs I repaired recently had 20mm I think they intended to use longer dowels.

                    Comment


                    • #11

                      Re: Floating tenons - pros and cons

                      I don’t use floating tenons because aside from hand chopping mortises, I don’t have a method of making mortises in the ends of pieces.

                      I normally use a hollow chisel mortises and shaper for the tenons...Rod.
                      Les Groeller likes this.
                      Work is the curse of the riding class.

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                      • #12

                        Re: Floating tenons - pros and cons

                        We have had this particular discussion on the Forum before with most folks really committed to whatever method they use. The science of joinery is mainly ignored by us woodworkers in favour of what is at hand or what we blew our hard-earned cash on but there are some facts that came out in the last discussion that I will review.

                        The major difference between a real tenon, a dowel or a floating tenon is unrelated to glue but rather to the the big difference in the load path between a floating tenon and the continuous fibres of a real tenon. A floating tenon is a discontinuity that creates a prying action in the long grain of the parent wood when the joint is in shear whereas the real tenon acts as a reduced beam of the parent material and will be stronger in bending and shear given the same cross sectional area and thickness/height distribution. Whether that would make any difference in a furniture application or not depends a lot the geometry of each individual join and on the overall geometry of the piece. Does that make any difference in Randy's application? One cannot tell without seeing the relative distribution of the material remaining so there is no one-size fits all answer.

                        Modern glues manage to carry the load much better than their predecessors so, assuming a reasonable fit, the long grain to long grain adhesion could be good to excellent. Irrespective of that fact, neither a dowel nor a floating tenon (really just another form of the dowel) can develop the same shear and bending capacity as an equal sized tenon of the parent material. Would such a thing be strong enough? Probably, especially so if a dowel was carrying the shear and bending loads across the joint in the first place.

                        Ken

                        djnelson, stotto and 3 others like this.

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                        • #13

                          Re: Floating tenons - pros and cons

                          Ken, you explained much better what I was trying to say.

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                          • #14

                            Re: Floating tenons - pros and cons

                            I have made countless (well, not really, as I'm sure they could have been counted...) mortise and tenon joints. And many of those were angled joints, in my years as a cabinetmaker and now, serious hobbyist, so feel qualified to throw in my two-bits here.

                            I know that several traditionalists here will swear that regardless of the angle of the joint, only a tenon machined from the end of a rail will provide optimal strength to the joint. I tend to think that like most things in life, joinery is not an absolute issue. Case in point, an angled joint where the tenon must run non-parallel to the grain of the rail. In such cases, as one who has made many chairs over the years, I have found that a floating tenon makes for a stronger joint. But for any joint where the face angle is less than 10 degrees, the traditional machined tenon from the end of the rail is the ideal choice.

                            But let's not fool ourselves here. We don't live in an ideal world, and regardless of whether you're a professional making a living at this, or an amateur, there are only 24 hours in any day. And floating tenons have proven themselves up to the task of dealing with, as Ken put it, the "prying action in the long grain of the parent wood". If you don't believe me, then do your own test. Further, in Europe, where they are perhaps more anal about accepting new techniques until they've been proven to work effectively in the shop, they have embraced floating tenon joinery. And that, my friends, is why machines which make mortises for floating tenon joinery are so common in shops - professional and amateur alike - today. Not just in Europe, but on this side of the pond as well. They are the fastest way to create a mortise and tenon joint in most shops. And the most popular mortiser on the market today has to be the Festool Domino. I use my model 500 for most of my smaller mortising requirements and turn to my slot mortiser when a larger and more roboust floating tenon is called for, or on compound angled joints or any size. But, that's my choice and I certainly won't disagree with any one else who prefers to use traditional mortise and tenon joinery. To each his/her own.


                            Originally posted by KenL View Post
                            We have had this particular discussion on the Forum before with most folks really committed to whatever method they use. The science of joinery is mainly ignored by us woodworkers in favour of what is at hand or what we blew our hard-earned cash on but there are some facts that came out in the last discussion that I will review.

                            The major difference between a real tenon, a dowel or a floating tenon is unrelated to glue but rather to the the big difference in the load path between a floating tenon and the continuous fibres of a real tenon. A floating tenon is a discontinuity that creates a prying action in the long grain of the parent wood when the joint is in shear whereas the real tenon acts as a reduced beam of the parent material and will be stronger in bending and shear given the same cross sectional area and thickness/height distribution. Whether that would make any difference in a furniture application or not depends a lot the geometry of each individual join and on the overall geometry of the piece. Does that make any difference in Randy's application? One cannot tell without seeing the relative distribution of the material remaining so there is no one-size fits all answer.

                            Modern glues manage to carry the load much better than their predecessors so, assuming a reasonable fit, the long grain to long grain adhesion could be good to excellent. Irrespective of that fact, neither a dowel nor a floating tenon (really just another form of the dowel) can develop the same shear and bending capacity as an equal sized tenon of the parent material. Would such a thing be strong enough? Probably, especially so if a dowel was carrying the shear and bending loads across the joint in the first place.

                            Ken
                            All the best,

                            Marty

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                            • #15

                              Re: Floating tenons - pros and cons

                              I am not sure that we are comparing apples to apples here so let me attempt to clarify what I said previous(acknowledge before I start that I thought that the science was pretty clear in the first explanation!). Number 1 - Joints designed for floating tenons are adequately strong, no doubt about that and so were dowel joints until the glue failed or dried out. The argument about them being just as strong as a properly designed and executed moritce and tenon joint in the same application is factually incorrect but, important point here, the difference is generally moot since Number 1 holds true. When floating tenons are retrofitted to repair failures, Number 1 may or may not be true and often is not.

                              Europeans have embraced Dominos to expedite their manufacture, end of argument. They are keen on particle board and lots of other technologies that we hobbyists generally eschew too. That does not imply any superiority of strength over a traditional joint a fact which can be readily demonstrated by application of simple mechanics to the calculation as I did in my explanation before. We could argue til the cows come home about the angled mortice example but a floating tenon simply transfers the potential failure site from one side of the joint to the other, it will not be any stronger.

                              As some of you no doubt recall from the last go around on this subject, I do not own a Domino and will never cut enough mortices to justify the cost of one either. If you have one, of course you should use it where it is applicable. Please don't confuse mechanics with convenience is all I am saying.

                              This is off topic but I am going to indulge in an example to reinforce why I learned to execute traditional joinery. I make a lot of things where an oversized machine like a Domino would be utterly useless; things like this walnut and brass business card holder for one of my children as an example (the vertical pieces are morticed into the base and are back pinned (with brass) to ensure that they never fall out even if knocked off his desk by accident. For size reference the brass rods in the piece are 3/32" dia):
                              Click image for larger version

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                              This joints in this 4 inch long piece are huge in comparison with some of the mortices I have made for spoon stands and other Objets d'Arte that sneak out of my workshop periodically.

                              Ken

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