I agree. It's simple, it's elegant, it works well, it's handy as heck.
Couple things to always remember...
First, all router bits are NOT made alike - even two router bits from the same manufacturer, with the same brand name and the same size markings, will not necessarily be exactly the same diameter. When you build a jig like this one, you MUST build it for ONE ROUTER BIT and use the SAME bit with it - not one "just like it" EVERY TIME for it to work really right. It's worth doing to buy one bit dedicated to cutting dadoes & grooves with this jig and use that bit for nothing else. Heck, rout a pocket right in the jig someplace & store that bit IN THE JIG.
One workaround, of course... :) After the jig is made and you've used up the dedicated router bit, you COULD still use a short top-bearing template-follower router bit with it - say a 1/2" bit with a 1/2" top bearing, If necessary, you can steal a 1/2" top bearing from a longer top-bearing trimming bit to fit a short 1/2" template follower you've bought that came with a 5/8" bearing.
Second... be AWARE that only seldom is a router's base truly concentric with the bit; the bit will always be offset a tiny bit to one side or another. So... when you make the jig, take note how the router is positioned and always run the router through in that orientation. Say the left handle rides the fence on your first pass through (which cuts the bearing plate to its final width)... always make sure the left handle rides the fence when you use the jig.
I've made up some square (and rectangular) router base plates just to ensure the same exact orientation every time - that may be something you want to do.
Last... these notes are really for pretty fine precision. If your need for precision isn't yet that great, ya can disregard most of what I've written. :)
EDIT: Oh, yeah. One last thing. A "dado" goes across the grain. A "groove" follows the grain. :)
-- Tim --
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Robert "Limey" Bolton Memorial
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