I've done a lot of "regular" mortise & tenon joints, but am moved to try
loose tenons for my next project (a dining room table). Are there any
situations where loose tenon joinery is NOT recommended? Any hints or
The only time I used them was when making a bunch of passage door. Worked
The mortices were 1/2" x 2" deep in both rails and stiles, cut with a spiral
bit. Duck soup to make the tenons...prepare a long piece to width and
thickness, round over all edges as needed to fit the mortices, cut off a
bunch to correct length. I did make them a tad shorter than the combined
depth of the mortices and cut a shallow groove along one side with a thin
kerf table saw (before rounding over) to provide a place for excess glue to
Only caveat I can think of is to be sure to cut the mortices so that they
are either centered (two passes, one from each side) or offset from the
Built a lot of tables and chairs using loose tenon joinery here.
You will find that throughout every test published thus far the
difference between loose and integral tenon joinery is basically
negligible with modern glues.
The big plus with loose tenon, in my experience, is the ability to batch
cut your aprons and rails, thereby gaining a great deal toward the
squareness of your project, as well as the cost effective use of
IOW, I would not hesitate to continue planning to use loose tenon
joinery on your project.
My tuppence, FWIW ...
I agree that loose tenon joints are not really much weaker and
obviously these tests you mention (I haven't seen them) seem to prove
that out but I have seen some 200+ year old windsor chairs that had
proper mechanical fits and they are still going strong. I don'tthink I
could say the same about 200 year old Titebond x but check back in 200
years and maybe my opinion will change.
Likewise, I have handled some 200 year old pieces containing much
"pocket hole" joinery that is standing the test of time, yet the debate
still rages on that joinery technique ...
Until I see some evidence that loose tenon joinery must be pinned on
both sides in order to stand the test of time, it will remain
conjecture/supposition, without support, in my book.
... no disrespect intended, you're too damn good of a furniture maker,
and, unlike many of those proffering advice hereabouts, we get to
actually see pictorial evidence that that is so on your website ...
No problem, just spouting opinion.
I have a dirty little secret that I love pocket screws. I've built
many a coffee table and end tables that use them exclusively and I
have every assurance they will stand the test of time. I do also count
on the sort of box truss concept of the geometry to contribute to the
strength of the structure. I did a sort of Federal pencil leg table,
that I still use myself and those pocket screw connections from leg to
apron surely will not last. I am very careful with that little piece
but it looks nice.
Loose tenons don't work well in cases where the tenon shoulders would
normally be very thin. Consider a table apron going into a thicker leg.
With a regular tenon you could use a 1/8" shoulder (just enough to
cover any imperfections) to keep the tenon as thick as possible for
With loose tenons you would be forced to use a thicker shoulder to keep
your mortise walls thick enough. This translates into a thinner tenon,
and possibly a weaker joint.
To the OP ... Chris is correct in that regard, however there is alway a
point where common sense and practicality span the gap of the
theoretical proving of a negative ... use of the traditional "1/3 the
thickness of the rail/apron stock" for tenon thickness and the above
generally becomes a non issue on most projects, loose or integral tenon
That said, If you feel you need really thicker tenons for joint
strength, then your project would likely benefit from thicker stock for
your aprons/rails to begin with.
Besides, departing from the ubiquitous "3/4 inch stock" mindset of most
woodworkers today will generally do wonders for your project, in both
looks and durability.
My understanding is that the basis of the "1/3 thickness rule" is to
ensure that the mortise sides aren't too thin, so it's actually the
thickness of the piece being mortised that matters, not the piece being
tenoned. If the two pieces are the same, this makes no difference. If
the mortised piece is thicker, this can make a big difference in tenon
Of course, this is only important if strength is an issue.
During my time on the design board, it was common practice when
designing a knuckle fitting for a pivot on the end of a cylinder for
example, to make the knuckle twice the width of the pin diameter, thus
insuring that the knuckle had the same cross section in shear as the
The 1/3 rule for M/T joints in wood is would appear to be based on
similar design concepts.
Depending on what device (machine\tool) you have to cut the mortises
they can be a real rpoductivity and accuracy help.
However, important consideration is what stress will the joint need to
accomodate. A classic pinned mortise can resist an enormous amount of
twist, pull and down forces and even if the glue fails, after 100
years that mechanical joint of one continuous piece of wood (tenon)
held inside another (mortise) will still have most of it's integrity.
A loose tenon on the other hand, unless it is pinned on both sides
will not have the same longevity and ability to withstand the racking
Table leg to apron connections take lots of stresses. Chair rail and
spreader connections also. Maybe a picture frame where no stress is
really present or a box where the basic geometry adds to the strength
reauire no second though but structural type connections need to be
Tough to cite anything related to long-term joint durability. It would
require some realistic form of accelerated aging. Looking at surviving
pieces, we know that pinned joints have lasted a long time. We don't
know how loose tenons hold up over hundreds of years.
All glue fails eventually. This could be accelerated on a wide apron if
the loose tenon is of a species with different expansion rates and
humidity swings are wide.
However, this is stuff that only matters if you're building for the
really long term. And in that case, yellow glue probably isn't the best
choice since it isn't repairable. Hide glue, resorcinol, polyurethane,
epoxy, or plastic resin are all better choices in this respect.
As I said, " Long after the wood has returned to compost, epoxy and
still be there, thus what's to repair?, and that includes the
conditions described above
As for heat degradation, by the time the epoxy is softened, the wood
will be scorched.
If you are going to use epoxy as a coating, then UV protection is
If you are going to use epoxy as an adhesive, no UV protection req'd
since only the outside edges of the joints are exposed.
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