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It's just a
mortise and tenon...so what is the big deal? The only thing new for me is that the tenon
was cut with two blades at once, leaving a perfect fitting tenon. And what's more, I can
make perfect fitting tenons from now on, without trial and error setups.
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This is not a new idea...not at all. It
has been subject of many magazine articles over the years. This last week, someone in an
on-line forum raised the question and it was a gentle reminder that I should take the time
to figure it out—after all tight tenons are good. So if you are interested in tight
tenons every time without trial and error setups, here is what I did.
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First, I started by setting up the
mortiser to do 3/8" mortises. Any mortise size could work but almost all the
mortises I do are 3/8" wide and 1" deep.
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My plan is to use the two 6" dado
blades and to separate them with spacers. Here I am getting an approximation of what
combinations of spacers are needed to fit snugly into the 3/8" mortise.
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As a starting point, I select two blade
stabilizers and 2 brass shims as the first assembly.
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I even unmounted the mortising chisel
and brought it to the saw thinking that would help me set the spacer package. It got me
close, but only cutting samples would work to get the spacer width exactly right.
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I am setting up the Delta Tenoning Jig.
With one blade, it stays a respectable distance from the metal base. With two blades, the
one blade gets very close. To remedy this, I use a piece of 1/4" plywood as a spacer
to fit on the jig. That 1/4-inch makes the difference.
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For the moment, I have mounted the
board with the mortise and am using it to fine adjust the tenon placement.
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Now with a new board in place, I make a
trial cut. At this point I really am only trying to perfect the spacer bundle to give me a
tenon that is a "glove-tight" fit to the 3/8" mortise. You can see one
sample at the left. In fact, I made 7 sample cuts changing the spacers a few thousandths
at a time. This is more sample cuts that I usually do but I am interested in finding
the perfect spacer package and glove-tight tenon.
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