Nearly a week ago, Frederick Walker asked:
>Can anyone point me to (or tell me) the proper way of cutting the mitered
>breadboard ends (in a Galootinous fashion) that are often seen on slant
>front secretaries?
I went through my various references, hoping to find one which substantially
answered Fred's query. Not having come up with one, and thinking this may
deserve some discussion on the list, I've decided to attempt a somewhat
detailed reply.
Clamping, the historic trade term for this feature, can be done in a variety
of ways (simple tongue & groove, and dowels, as examples); but I'm assuming
that Fred is referring to the haunched mortise and tenon variety. A few of
my older references have good drawings and a couple of layout hints; but,
invariably, they gloss over the specific difficulties of executing this
particular configuration. (If someone comes up with an older detailed
discussion, I'd love to hear about it.)
First, a bit on layout.
Some of the older references suggest using the pre-formed mitered clamps as
layout patterns - knifing around them while they are in place on the surfaces
of the main panel. Not having read this before, I haven't tried it; but I
think it's a good idea. The primary advantage, as I see it, is that any
discrepancy, however slight, from a true 45 degree miter, will be auto-
matically compensated for in the layout. My only concern with this
approach,would be to have the jointed and mitered surfaces truly
squared to the
reference surface of the clamp. This should minimize discrepancies in layout
from the front to back surfaces of the panel. Another obvious aid would be to
have the panel stock carefully squared and trued up at the desired final
length.
Also, at least one of the illustrations shows the miter joint held back just
a bit from the front edge of the main panel. Again, I haven't tried this, but
think it would be a good idea if you have the luxury of, temporarily, leaving
the panel a bit wider than the desired final dimension. If the miter comes
exactly at the corner of the panel it can be fairly fragile and unforgiving
as one does the final trimming. I would be careful to keep the set-back from
the corner exactly equal at both ends of the main panel (maybe between 1/32"
and 1/16"?), and then carefully plane that edge of the panel to bring the
miters to the corners after the clamp is glued and pinned in place. This
would help keep the final clamped panel square.
Having defined the thickness and location of the tenons/haunches and
mortise/grooves with a mortise gauge, the next order of business is the
removal of the waste to create the material for the tenons and haunches on
either end of the panel. Obviously, the presence of the miters precludes
straightforward sawing or planing operations to accomplish this. So, the
object becomes to effectively isolate the waste areas, and then remove it in
as expeditious a manner as possible.
One strategy to isolate the waste would be to bore a few adjacent or over-
lapping holes near the junction of the knifed lines. A forstner bit would be
ideal for this, being careful to go as close to final depth as feasible. The
cavity formed by this operation (possibly with some clean-up with a chisel)
will provide a space in which to run the toe of a back-saw to make initial
cuts along the shoulders. Some simple means (such as some strategically
placed pieces of masking tape) of determining the depth of the saw cuts
would be advisable.
Personally, I'd leave a little waste inside the knife lines for later clean-up
by vertical paring. Alternatively, one could form a small V-groove by paring
with a chisel along the waste side of the knife line; or, simply make use of a
trued-up batten to guide the cuts.
Once isolated, the waste removal can begin in earnest. A couple of methods
come to mind. (I'm hopeful others will have better ideas.)
The first would be to split off pieces of the waste by driving a chisel into
the end-grain. Needless to say, this will only work if the material
is relatively straight-grained and has no significant run-out. In
other words,
if one were using figured or wild-grained material, this technique is not
going to be very useful.
The second technique is the use of a bench gouge. The ideal would be to use
a gouge which would cut almost deep enough as the wings of it's cutting edge
are just even with the surface of the material. As long as you keep the gouge
level, laterally, it will be somewhat self gauging if you have surface material
on at least one side against which to judge the depth. I would use a mallet
and go at it in a very methodical manner - mostly going cross-grain. This
allows for a great deal of control, yet accomplishes waste removal in a
straightforward and measured manner.
The final clean-up can be accomplished with a router. The outboard end of
the router can be registered upon a bit of the waste left at the outer
extreme of the tenon material or a batten of the same thickness as the panel.
If you have left some waste inside the knife lines, this would be a good time
to clean it up. Careful vertical paring, registering the chisel in the knife
line for the final cuts, should be effective, working either free-hand or
with a batten to help guide the cuts.
The tenons and haunched areas can then be determined and cut out - to be used
as a template for the mortises.
The chopping of mortises is, then, fairly standard. Personally, I prefer
chopping the mortises prior to ploughing the grooves for the haunches. Plough
plane irons tend to run slightly oversized and may obliterate the gauge lines.
The last remaining difficulty is the manner of affixing the clamp to the
panel. The tenon nearest the miter, and the miter itself, can be glued as
well as pinned. However, since we have cross-grain construction, it is best
to allow for expansion and contraction of the panel relative to the balance
of the clamp.
My approach has been to use pins at the remaining tenons, slightly off-setting
the hole in the tenon toward the shoulder (a shy 1/32"). This helps pull the
clamp tightly into the shoulders. Once this hole is bored, I then knife short
lines at the tangents of the hole parallel with the shoulder, and elongate the
holes into short slots to allow for movement. These can be opened up with a
pad saw if the tip of the blade will enter the hole, or simply chopped out
with a chisel. This movement allowance can be calculated using the tables and
formulas in Bruce Hoadley's _Understanding Wood_. Needless to say, the
mortises need to be elongated a corresponding amount.
Hope this helps and I'm hopeful others will share their ideas.
Don McConnell
Knox County, Ohio
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