Recently I developed some software to assist in making box joints on a router
table using a simple pivoting fence. The software prints out a custom template
for setting the free end of a pivoting fence. Unlike the methods that utilize a
guide pin to set each slot position from the previous slot, this method has no
cumulative error. And a pivoting fence is a lot simpler to make than a
parallel-moving fence indexed by lead screws. I have found it particularly
useful to print several templates with slightly different pitches to fine tune
the tightness of the box joints. I would appreciate comments on my software.
It is available on my website at www.tunelab-world.com/router.html
By the way, if you don't want to try the software, at least look at the pictures
in the manual, also available from that web page. It shows the setup and a
sample box joint that was made using that method.
Looks cool. It took a bit of re-reading to figure out what each of the
parameters actually did, but eventually it all made sense.
I wonder if you could get a more accurate starting point by doing a few
cuts with the actual bit in a scrap of the project wood and measuring it
Personally I like idea of the dovetail jig template with the
adjustable-diameter bushing. I've never actually used one though, and
it's definately more expensive...
There are several ways to get an accurate starting point, and the way you
suggest is certainly a good one. I assume that by setting the starting point
you mean deciding exactly where to tape down the template. Because once you
tape down that template, all the slot positions are determined. Of course
moving the template is very easy if you use masking tape and want to make some
fine adjustments to the offset.
The setting of the starting point is actually not a critical parameter. If the
template is moved by 1 mm., then all the slots in the box joint will be moved by
that same 1 mm., but it will still be a perfect box joint.
One aesthetic consideration is the size of the top and bottom fingers in the box
joint. If the width of the wood is not an exact multiple of the slot spacing,
then the top and/or bottom fingers must be partials. That can look OK if the
partials are 1/2 to full size. But if a partial finger is too small, it looks
like a mistake, and it might even break off during routing. Fortunately there
is usually a starting offset that will ensure top and bottom fingers are of
substantial width. Or I suppose you could adjust the dimensions of the project
to match to the nearest multiple of the slot spacing. But that seems like an
unnecessary concession to have to make. You can see that the sample box shown
at the end of my manual has partial-width fingers at the top and bottom.
There is a limit to how far you can move the template, though. Theoretically,
there is only one right place to tape the template to the table and still have
all the tick marks on the template fall exactly in line with the edge of the
fence. But in practice you can move the template a little and still get good
results. If you move it so much that the tick marks are not exactly parallel to
the edge of the fence, then you can simply pay attention to where those tick
marks cross the X-axis base line, and position the fence so the desired
intersection point is just at the edge of the fence. If you want to make larger
changes in the offset, instead of moving the template, it would be better to
print out a new template with a different "Router Offset" parameter. It is not
necessary that the Router Offset parameter be exactly half the diameter of the
router bit. Doing so just makes it easier to position the template by adjusting
the fence to just kiss the router bit and then sliding the template under the
fence until the "0" line lines up with the fence edge. But if the Router Offset
is set to slightly different number, you could still use the bit to position the
template. You would just use a spacer or gauge block or use calipers instead of
having the bit just kiss the fence. That is why the parameter is labeled
"Router Offset" and not "Bit Radius", even though in many cases that's just what
No, actually I meant as a value to input for the "tick mark spacing"
since it is dependent on the size of the slot cut by the router bit.
(The same holds true for "router offset" to a certain extent, with the
caveats from your email.)
Your manual has a section on how a worn 0.25 inch bit actually cut 0.241
slots. I was simply suggesting making some test cuts to see what the
router bit actually cuts instead of proceeding by trial and error.
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