Box-o-matic: a quick-n-dirty indexing finger joint cutter
for a tablesaw.
This is the jig for automated finger joint cutting on
the tablesaw. Probably the operation is fairly obvious. The modified fence with a perpendicular
standoff only moves laterally. The standoff has a threaded insert through which the 20 threads
per inch screw runs. The other end of the screw butts against the carrier, which is L-shaped.
Rotating the index handle pushes the carrier to the left. The staves of the box are c-clamped in
place, but I didn't include the C-clamp because it is HELL to model in Bryce.
The advantage of this over a standard router table finger jig is that this can cut not only any
thickness of wood, but can also precisely determine the quality of the fit. I initially calculated
that, given the thickness of the tablesaw blade, my turn procedure would be cut, rotate the
handle three times, cut, rotate the handle eight times, cut, rotate three times, cut, and so forth.
This produced a beautiful joint that required serious hammering to press together.
My second try, for a looser fit, used the procedure cut, rotate 3 1/2 times, cut, rotate 7 1/2 times,
cut, and so forth. I calculated that this would add twelve thousandths of an inch of clearance to
the joint. It was loose (though even).
So I finally ended up by doing cut, rotate 3 1/4 times, cut, rotate 7 3/4 times, and so forth. This
makes a joint that slides together with hand pressure and holds quite tightly.
I like it that I can easily machine wood to within 0.006" -- one eighth of a turn of the index handle.
It takes about three to five minutes to do each end of the slats. Since they're all clamped together,
they're identical. Flip the batch and run the other side -- maybe ten minutes of work per box.
Then it's just a matter of cutting in the rabbet for the plywood bottom, and of course, FINISHING.
The final intended product.
This page created 3/15/02, last modified 3/23/02
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