I'm looking at the current issue of
popular woodworking and I'm puzzled
about the length of mortises they're
recommending for a face frame
construction. The piece can be found here:
A better pic can be found here:
On 2 3/4" stiles they are recommending 1
1/4" mortises for tenons from the rails.
The stiles are 3/4" thick. All maple.
It's hard to tell from the picture, but
there are 5 rails, 5.5" at the top, 3"
at the bottom and 3 that are 1 1/4" for
the drawer dividers.
The entire piece is 78" tall and 21"
wide. 10" deep.
I don't have a mortiser. I have straight
chisels and a router. I don't know if I
can mortise that deep with the router,
but if it's necessary I guess I could.
My question is: Do the mortises have to
be that deep for this kind of
construction, or could I go with
something shallower? If shallower is
acceptable, would it be ok to go 3/4"?
In this case the face frame is there to help resist racking forces. In
general, longer tenons are stronger. The standard rule of thumb is 5x
the thickness of the tenon. I'm guessing that they're using 1/4" thick
With the right bit you can go a lot deeper than that. I recently made
some 2" deep mortises with a router and chisels, and some more with a
drill press and chisels.
Going shallower will weaken the joint. The shallower you go, the weaker
it will be.
Deeper is better because you provide more surface for the glue. The
shallowest mortises I do are 7/8"s for crest rails - which I generally
pin. If you have a plunge router and a 1-1/2" bit, you should have no
problem making 1-1/4" mortises.
Ok, that was pretty unanimous. 1 1/4" it
is. The door is 44" x 15 1/2". I'm
guessing that fits into your larger door
category, so it'll have 1 1/2" mortises too.
The tenon is 1/4", so the 5x rule is
being followed. That wasn't a rule I
knew, but it seems easy enough to remember.
Thanks very much., guys. I don't know
when I'll get to this project, but I"m
glad I asked this. I've done a few
mortise/tenon joints, and read up on
them, but never really knew how long
they should be. I've always just
eyeballed before. This makes more sense.
I would not believe a damn thing I see in print, particularly from many of
the "experts" writing "how to" articles in some of these woodworking rags in
just the last five years or so. :)
Instead, stick with traditional "proportions" for joinery parts whenever
possible. When it comes to mortise and tenon joinery there is ample evidence
of traditional methods standing the "test of time"
Looking at just the picture of the project, I see nothing that would make me
deviate from the above, and below.
For future reference, the time honored/traditional "proportions" for a
standard "stopped mortise and tenon" joint:
~ Tenon thickness of a standard "stopped mortise and tenon" joint is
approximately 1/3rd the thickness of the rail, and usually runs the entire
width of the rail (except when it would weaken the stile/leg, then "double
tenons and mortises" are preferred).
~ The depth of the mortise of a standard "stopped mortise and tenon" joint
is approximately 3/4th the width of the stile/leg.
It is _always_ a good idea to get as close as possible to these
"proportions" if you want your work to be around to be appreciated for many
Strictly my tuppence, and the way I would spend it ...
Your tuppence is good enough for me.
From your post and others, I have a
bunch of easy-to-follow rules that now
make sense. Well, maybe they don't make
perfect sense, but I'm not about to
argue with hundreds of years of trial
FWIW, You've just posted what Chris Schwartz writes several times a
year, with one clarification.
Machine made mortises in 3/4" stock are often 3/8" thick, due to the
fragility of 1/4" mortise machine tooling. The advantage of a 1/4"
tenon when hand cutting is there is less of a likelyhood of levering
out the sides, compared to a 3/8" chisel in 3/16" sides.
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