I'm between projects at the moment and I'm contemplating the next one. I
try to design in a new technique here and there to improve my skills.
I've been flirting with the idea of through tenons. Given that I have
yet to make even a blind mortise and tenon joint, this may be premature,
but I'm tossing around ideas in my head.
I've got some ideas about how I could make tenons given my limited tool
set, and I figure a plunge router (which I don't have yet) and a
template would take care of a *rounded* mortise. I'm wondering how you
guys square off the mortise. I assume that unless you have a dedicated
mortising machine, you use some sort of chisel(s), but what kind?
Do you use anything special, or just regular chisels? I've seen a corner
chisel, if that's the right term. I don't mean the kind they sell for
hinge mortises. It's a fairly long chisel with two cutting edges at a
right angle. I also see square chisels, which look very much like the
hollow chisels that are used in dedicated mortising machines, but with a
handle to be struck with a mallet. Lastly, I've seen mortising chisels,
which seem to be twice as thick as regular chisels.
Regular chisels for me. If it's a thru mortise, cut in from
both sides so the cut is clean at the edges. If the chisel
strays a little in the middle of the mortise it's no problem.
Corner chisels look like a neat idea, but they're hard to
find and hard to sharpen, so a regular chisel is just
Decide whether you want square corner or rounded mortices.
Cut the mortices.
If round, a plunge router works fine. Cut the tenon square, use 1/4 round
router bits to round off tenon edges. You can't use the router to get all
the way to the shoulder but what remains can be done by hand easily with a
knife, rasp, whatever. You could also use loose tenons, easiest of all.
Size the tenons according to the 1/4 round over bits available; i.e., if
tenons are 1/2" thick, use 1/4 radius bit; if 3/4" thick, use 3/8" bit; etc.
If square, you can remove most with a drill bit or router, squaring up with
a hand chisel, knife or file. You could also saw out the corners with a
scroll or coping saw. You could do the whole thing by hand as John
explained (there are special, longer mortising chisels for that purpose).
You could drill them square in a drill press with mortising bits...those are
a bit in a hollow chisel...the bit removes most, the chisel shears off the
corners as you lower the bit, same as a dedicated mortising machine. On a
drill press, you need a fence and a mortising attachment to hold the work
solidly in place.
OP was speaking of thru mortises, so he'll probably want them
square. I don't think I'd do a rounded mortise unless I was
going to do a very long tenon, and put a peg thru it on the
I think it was actually Scott who suggested a mortise chisel.
Cutting mortises that way takes a fair bit of practice.
While all the methods you list are good, for someone starting
out with limited tools I would go with either a router and
template, or drilling a sequence of holes, and in either case
using a normal bench chisel to clean up.
Something else to think about if you want to do floating tenons with a
It's possible to do floating through tenons, with the visible part
square, giving you a traditional through tenon look.
Because I use a Multi-Router for most of my floating tenon joinery, I've
done this a few times:
In the one shown I did inset the square part in the stile/leg using a
dedicated mortising machine for a shallow (1/4") square mortise, but you
don't have to.
Just make the visible square part of the tenon long enough for the look
you want, insert in both parts, glue and pin the joint with a
contrasting pin, and Bob's your uncle.
The part is that difficult to make once you get started, and there is
more than one way to skin the cat to fabricate them.
I make them square, then round-over the square edges of the floating
tenon with a pattern makers file to fit the round mortises cut in the
stock with the Multi-Router.
Traditional look and strength, modern tools...
AND to expand on that a bit.... you can also do trough tenons and sand
them flush with the piece that they are going through, the exposed side.
Don't worry about appearance. Cut a false tenon to glue over the
actual flush sanded through tenon. It can be slightly larger than the
actual mortise to cover the "real" joint lines.
Great idea! And affords the sticking out portion of the tenon to be a
longer length than my suggestion above.
I was thinking about that. Karl's drawing shows a loose tenon that does
need to be inset in a mortise that is squared off, at least to a certain
depth. I see that you could do away with that, by making the "square"
part only as thick as the visible section. But it strikes me that that
would make for a very thin edge, unless the visible section is to be
thicker than usual.
Yes, the visible part would be larger to your liking and would cover and
hide the actual mortise and tenon. For strength, floating tenons do not
have to a perfect fit except with the cheeks of the tenon being the same
as the mortise. Length is not so important, you have plenty of contact
glue surface on both sides of the tenon. Floating tenons typically do
not completely fill the mortise anyway, this gives you wiggle room. In
fact the Festool Domino has three width settings for it's fixed width
Domino tenons. Exact fit, and two progressively wider than exact fit
That would be what I'd say. You can cut the mortise with
a router, or by drilling the ends and a series of in-between
holes on the drill press (and chop out the bits between with
a chisel). Either of those are available to someone just
starting in woodworking, who wouldn't have a mortising
machine, mortising attachment for the drill press, or old
style mortise chisel.
The disadvantage is that it's obviously machine-made. If
the tenon is visible, and you want to emphasis your hand-
craftsmanship, then it has to be square. So you either
make a square mortise, or you do as Leon suggests and make
a faux tenon as a trim piece (which, honestly, to me sounds
like more work than making the mortise & tenon square).
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