Router base tune-up for inlay work

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Blog entry by John8059 posted 01-31-2009 08:59 PM 1282 reads 1 time favorited 0 comments Add to Favorites Watch

Since it is a little too chilly to work in my shop today, I’ll do a little virtual woodworking to get my weekend fix. I am working on a coffee table with a complicated veneer pattern and inlay banding. Below is the actual top veneer taped and almost ready to glue to the substrate. Since you only get one shot at cutting the grooves for the inlay, I spent a lot of time planning! One thing that concerned me was that I cound not use the flat edge of my router base everywhere so I had to rely on the rounded portion of the base everywhere. That meant that if the rounded edge of my router base was not perfectly equidistant from the bit throughout its entire range, I could have “bad intersections” and even curved or wavy inlay if I rotated the router along a straight cut.

I used a 1/4” bit to plunge a hole in a piece of scrap. I turned the bit around so the cutter was in the collet and the shank sticking out. I plunged the shank into the scrap and began to rotate the router. I found that the base was as much as 3/64” out-of-round. To correct the problem, I repeated the above in a 1/4” thick piece of scrap that was large enough to clamp to 3 edges of my router table. I set the table router up with a 1/2” used 3-blade carbide trim bit sticking up as high as needed. I plunged a 1/4” hole in the scrap, reversed the bit, and clamped the scrap down so the static router’s base was barely touching the trim bit. I rotated the static router so the flat edge of the base was facing the table router bit and turned it on. I gritted my teeth and rotated the static router so the trim bit would engage the rouded portion of the base. No problem! The carbide bit cut through the plastic base and aluminum like butter! It repeated this a couple times moving the static router closer to the trim bit until the entire base was truly equidistant from the center of the collet. You can see the newly-machined edges in both the plastic and aluminum surfaces of the base

With the router base “true”, I could now use the uniform distance from the collet center to the edge of the base to make some spacers to help me locate the fences that would guide the router to cut the inlay grooves. In the picture below, you can see the fences – aluminum straight-edges. They provide for the outer-most shape and the thin maple spacers act as stops to prevent the router from cutting all the way to the corner. For the cuts up the legs of the table, the maple spacers would be rotated 90 degrees and moved up to the top. The maple spacers also provide the edge to guide the router along the path for the corner designs. You can also see a thicker L-shaped guide (not thick for any reason) that acts as a stop for one of the corner detail grooves and a surface to get the short groove that leads back to the long outer grooves – cut using the aluminium guides. If you think this sounds confusing, you should have been me lying in bed trying to visualize this!

Here is the result of the first completed panel. Once the plywood and glue you see gets cut away, you should be able to see one side of the coffee table take shape. A closer look at one corner shows six perfect intersections where had I not taken the time to true-up the router base, you would be looking at ugly patches to cover up mistakes. Pardon the blurry picture and note that the ebony squares are (at least for now) proud of the surface by about 1/16” creating shadows and causing them to look even more blurred.

I’ll be adding more of this project to My Projects if you are interested in seeing how it progresses. Thanks for looking!

-- Cuz

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