Generic router mount for guide rails

slb

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Apr 2, 2008
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Here's an inexpensive and easy to make jig to let any router work with Festool guide rails.  It uses half of a block of 3/4 inch UHMW plastic that can be obtained from many stores, including Woodcraft and Rockler for about $25, and a couple of set screws.  The only shortcoming I have found so far is that the router bit needs to be long enough to reach through the thickness of the UHMW and still cut to the desired depth.  Since I use this jig mainly for dados, which are usually not very deep, that hasn't been a problem.  The UHMW is very slippery, but to keep the guide rails from shifting during use, I always clamp them to the stock.

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First mill the slot that will follow the ridge on top of the Festool guide rail.  It needs to be about 5/8 inch wide and 1/2 inch deep.  Tweak the width until you get a slightly loose fit onto the ridge (we'll take out the slop later).  The depth isn't critical, but needs to be enough to clear the top of the ridge when the guide rail and jig are both sitting on a flat surface.

Then decide where you want to mount your router on top of the jig.  It needs to be far enough from the slot that you won't cut the edge of the guide rail using the largest bit you want to use.  Unless you like to replace the anti-splinter edge, it's best to allow some extra space!  Drill a large hole (I used 1 1/2 inch) at the chosen location and also holes for screws to mount the jig onto your router.  My router has three holes in the base for mounting jigs, but only two of them would fit onto the 4 inch UHMW at the same time.  However, with two screws I haven't had any problem with the router wobbling on the jig.

Now mill out the large flat area that rides on the guide rail.  This needs to be wide enough to clear the edge of the guide rail when the slot is on the ridge, but is otherwise not critical.  The guide rail is nominally 5mm thick, but to get as close a match as possible, I crept up on it, gradually increasing depth until the jig would lay perfectly flat atop both the guide rail and an adjacent flat surface.

Countersink the two holes for mounting the router (couldn't do this before the flat area was milled).

Next drill two holes from the end of the jig toward the guide slot, stopping just shy of breaking through into the slot.  Thread a set screw into each hole.  When you tighten these screws, they each make a little bump in the side of the slot.  Adjust the screws to perfectly take out the slop without causing the jig to bind on the guide rail.  It the jig gets loose after use, just tighten the screws a tad more.

Finally, soften the edges of the jig, especially the end supporting the router.  I've found that UHMW is hard enough to mar soft woods such as pine!

Steve
 
I forgot to mention:  I scribed small lines into the sides of the jig at the center location of the bit to help with alignment to the stock.  With the router and jig sitting on top of it, the guide rail is pretty hard to move, so I also scribed a line into the end of the jig the same distance from the edge as the bit center falls from the edge of the guide rail.  You can set the jig on top of the stock with the scribe line at the desired center, put the guide rail up against the edge of the jig, clamp and go.

Steve
 
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