Loose tenon joinery

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 advice?

Reply to
John B
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The only time I used them was when making a bunch of passage door. Worked fine.

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 go.

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

*correct* side.
Reply to
dadiOH

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 expensive wood.

IOW, I would not hesitate to continue planning to use loose tenon joinery on your project.

My tuppence, FWIW ...

Reply to
Swingman

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 strength.

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.

Chris

Reply to
Chris Friesen

That's true. In every test I've seen (including one posted here, recently), the wood fails before the glue.

Reply to
-MIKE-

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 forces.

Table leg to apr> I've done a lot of "regular" mortise & tenon joints, but am moved to try

Reply to
SonomaProducts.com

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 notwithstanding.

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.

Reply to
Swingman

Reply to
SonomaProducts.com

Cites please ...

Reply to
Swingman

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 ...

:)

Reply to
Swingman

There are very few down sides... much faster and much less setup with a proper jig.

The only thing is to watch your reference side. That can be a slight problem until you screw up a few pieces.

There are MANY jigs out there to do this with...

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I've done a lot of "regular" mortise & tenon joints, but am moved to try

Reply to
Pat Barber

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 thickness.

Of course, this is only important if strength is an issue.

Chris

Reply to
Chris Friesen

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.

Chris

Reply to
Chris Friesen

SFWIW:

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 pin.

The 1/3 rule for M/T joints in wood is would appear to be based on similar design concepts.

Lew

Reply to
Lew Hodgett

I know hide glue is repairable. Are those others?

Reply to
-MIKE-

Long after the wood has returned to compost, epoxy and resorcinol will still be there, thus what's to repair?

Lew .

Reply to
Lew Hodgett

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 > S> > I agree that loose tenon joints are not really much weaker and

Reply to
SonomaProducts.com

Ask him, he wrote it.

Reply to
-MIKE-

Reply to
SonomaProducts.com

In my ken, hide glue is the only glue up to this point suitable for woodworking that will glue/adhere to itself. For a joint to be totally repairable at some point, as all glue joints will at some point fail, it helps to be able to dismantle the piece and hide glue is the best bet so far up to this century.

Epoxy is probably the best bet for longevity, but it is expensive, and forget about getting anything glued with epoxy apart; and urea formaldehyde glue may be the second best choice because it is much cheaper than epoxy, easier to use and because when it does fail, you can "repair" it, once, with epoxy, for another hundred years. :)

That said, I'm still using PVA's on most things, and urea formaldehyde glue (Weldwood, Urac 185 (?), etc) for long open times.

Reply to
Swingman

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