While at the Woodworking show last week I saw a demonstration for the Leigh
mortise/tennon jig. The guy doing the demo pointed out that furniture made
with mortise and tennon joints lasted 100s of years.
I can understand why an extremely well fitting joint was required in the
"old days" since the glue wasn't great, but with the glue available today
do the joints need to be as perfectly fitting? Craftsmanship aside, does a
somewhat rough joint significantly less strong than a perfectly fitted
joint over time?
Just curious if the $800 they wanted for the jig actually produced a
dramatically stronger joint.
No doubt. Of course, that was the most common method of joinery hundreds
of years ago too.
It would be better yes because if the glue is softer than the wood, it will
compress and the joint will loosen. If the glue is harder than the wood,
it may weaken the wood through racking over time. It may also be more
brittle and just crack.
Than what? I use a $99 mortiser and a homemade tall fence with a C-clamp
and get perfectly fit joints. In any event, while "dramatically stronger"
is subjective, I'd have to say no it does not. No way in hell it does
really if you take "dramatically stronger" to mean an order of magnitude.
Probably not dramatically stronger, but my understanding is that the jig makes
the use of angled and muliple tenons a great deal easier and quicker: I've
watched it being used, and the speed is truly impressive, once you learn to set
the jig up (not a small chore, though). The second majorpoint in the jig's
favor, or so it seems to me, is the possibility of replication. You can make
the joint, and come back a week later using the same settings and repeat the
joint withint whatever fractional or decimal accuracy is possible with the
"All you need in this life is ignorance and confidence, and then success is
I wasn't doubting that it made them easier, I was just wondering about
the strength. I've been using mortise and tenons in my furniture quite a
bit lately and I was curious if I was fooling myself into thinking it was
a stronger joint than it actually was. I just finished up a bed for my
oldest daughter and am starting on one for my youngest and I was hoping
my work would last long enough for them to be handed down once or twice.
firstname.lastname@example.org (Charlie Self) wrote in
Obviously haven't lived long enough to see if my many M & T joints will
stand the test of time, but I'd bet that most will, with one possible
caveat - those in chairs.
Chairs in particular have a lot of stresses put on them, and antiique chairs
have exhibited most of the M & T joint failures I've seen in furniture down
through the years ... very likely a result of a combination of things
besides the stresses, including the "glue" of the period, and the fact that
with wood, which moves, joinery is never a sure thing. Inarguable
manifestation of this observation is the cottage industry, of sorts, in the
guise of the "Chair Doctor" businesses.
That said, I've rarely seen a chair from the same period with _pegged_ M & T
joints that exhibits as much joint failure.
Strictly from this unscientifc observation, I'd infer that it may not be a
bad idea to peg those M & T joints you suspect might not hold up. It is easy
to do, can be a nice design touch, and was done quite frequently before the
advent of relying strictly on glue.
That brings up an interesting point... How many of you folks routinely peg
(Pin?) your M&T joints. I generally do, but I'm wondering if it's overkill.
Is there a reasony why pegs are not The RULE for chair joinery?
FWIW, My house has some 1860 vintage storm windows made with pinned M&T
joints. Where there were failures, it was not the joint, but the wood itself
that deteriorated due to 100 + years of harsh New England weather.
Depends partly on the glue you are going to use. If your are using
aliphatic resin glues (TiteBond Yellow Woodworkers Glue, for instance), is
is not gap filling. I will resist moisture better and hold stronger than
hide glue, but if your joint doesn't fit, it won't improve your joint.
Gorilla Glue, a polyurethane glue, purports to fill gaps, but the small
print is that the gap filling property is a very weak foam. So, if your
joints aren't well fitted, it's actually WORSE to use Gorilla Glue. Plastic
Resin glues, as used by David Marks on Woodworks, dry very hard (and
ridgid), are nearly waterproof, are gap filling, and have a very long open
time. So, if your are going to make bad joints, this may be the stuff for
OTOH, you don't need an $800 machine, which BTW, requires another $150 -
$350 machine to even make it work (the router). You can make perfectly good
joints with hand saws, planes chisels, drills and such. You can also make
perfectly good joints with just a tablesaw and a router. I saw a
demonstration by Yeung Chan on Chinese joinery. He disassembles and
reassembles a replica Ming Dynasty chair he made from a post card picture
and knowledge of Chinese joinery techniques. All the joints in the chair
but one he demonstrates in his book how to make primarily with table saw and
router, with very little hand work. When reassembled, he sits in his chair
and takes questions. No glue, no nails, no screws. Very solid. Important
point - He contends that a joint should not be too tight, or there will be
no room for the glue. That does not mean the joints fit badly, merely that
you can slide them apart and back together by hand (if you can figure out
which piece is not locked in by the other joinery). No malletizing
I looked at this jig pretty good before passing on it. Its price is just
ridiculous when you look at other methods of making the same joint. A decent
mortiser is anywhere from $175-250 and tenons are easily made on the table
saw, router etc. I shop built a very very simple tenon jig that if all my
tools and equipment worked as good as it does Id be delighted. Its just a
right angle fixture that slides on my table saw fence with a toggle clamp.
Took me about 20 minutes to build. That and a mortiser makes the joint quick
You don't need to glue a tenon. If the joint is properly loaded, all it
needs are a peg or two. Post and beam architecture, much less furniture,
attest to this.
When designing, your assembly should stand, as it will, without glue or
mechanical fasteners. Then the rest is gravy.
Most jigs are not devised to only make joints more precise, but for
repeatability, and EASE most of all. Why would you want to spend
more time making a joints thats sloppier than if you'd used the jig.
You can't afford NOT to buy that $800 contraption !
The software said it ran under Windows 98/NT/2000, or better.
So I installed it on Linux...
Now that's just plain silly. If you aren't doing this for a living, I can
think of a lot of things to do with $800. How about taking the family on
vacation this year and getting some perspective on life in general. I would
suspect the average audience in this forum is non-professional, so the jig
has no way to pay for itself. That doesn't mean it's not worth the $800.
It just means that it's not worth that much to me and a lot of other people.
For a professional, it is quite possibly a serious time saver, and whether
you like it or not we are all, in the end, paid by the hour. For a tool
junkie, it's a status item. For an amateur whose more interested in the
result than the journey, it may be worth the $800.
I, for one, CAN afford to NOT buy it.
Well I do make my living doing this kind of work along with being a general
contractor and builder of log homes. Cabinet work has been something I've
done on and off for about 20 years now. Now I'm not stating that to say I've
been doing it longer than anyone else. My point is that that overpriced jig
is not that much faster to justify the cost. And if you know what you're
doing you can make the joint just fine using one or more of many methods.
I've seen the demos, I got the video and I watched and helped a fellow
cabinetmaker use the Leigh. Its just not worth the cost. If it were to
substantially add time or quality to my job then fine its justifiable. If it
doesn't offer me either one of those things, its useless to me no matter
what kind of tool it is.
Dave, you OBVIOUSLY have not met either my wife or my wallet ;)
I agree that it would make the job faster, and if I did this for a living I
could probably justify it. For the work I do though, I think it will be a
long time before I can make the case to the CFO.
Also, it stands to reason if you have one or two jobs to do, its never
going to be worth the $800 jig. If I did this day in and day out, or
made a living at fine furniture making, perhaps I'd throw down $800
for said jig... But for hobby use, my delta mortiser is plenty, and I
can use the router, or bandsaw & chisels for the tenons.
The software said it ran under Windows 98/NT/2000, or better.
So I installed it on Linux...
I'm biased, since I have the Leigh mortise/tennon jig. It is as good as
advertised. I don't have a lot of time to handcut joints, nor do I want
to settle for joints that are *almost* right. The Leigh jig makes it
easy to make perfect mortise/tennon joints the first time. The manual
that comes with the jig is excellent. Setup time is minimal.
Repeatability is excellent. If you're serious about making mortise and
tennon joints, you'll want to at least try out the jig. It comes with a
thirty-day return priviledge.
(By the way, I have a Jet Mortiser, a Delta tennoning jig for my
Uni-saw, and about a dozen jigs that I've made for my routers over the
years. The Leigh Jig does the best job in the least amount of time.)
As far as a dramatically stronger joint is concerned. If you have the
skills/tools to make a tight fitting mortise/tennon joint, then you've
already achieved the ideal; however, if you need a tool that *helps* you
make a tight fitting m/t join quickly and repeatably, without the need
to clean-up with a chisel, consider the Leigh.
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