French Knot Walnut Inlay in Cork Floor

I took several pictures while doing this project because the Festool "system" surrounding the OF-1400 router was key to its success (yes, yes, you could make your own rail or do it by hand, but this was fast, easy, and, uhm, smart :)  I also posted this entry in a shorter form on FestoolOwnersGroup.com as part of a contest I won't win.

Here, I have my new entryway :)  I took 2 sheets of 1/8" luan plywood and cross-laminated them together to form a substrate that was water resistant and able to be directly attached to my slab foundation.  I covered it in a nice cork in a herringbone pattern; in dry-fitting the layout, I found the herringbone pattern didn't telegraph the seams as much as others.  I then laid out a French knot pattern with masking tape that by chance was very nearly the same width as my extremely bowed scrap of Walnut :)  Center stage is the OF-1400 router and a guide rail.  Those two made this process ridiculously easy.

To route the recesses in the cork, I'm using a 1/4" down-spiral bit.  My process is to route away the outside edges of the recesses then go back and eliminate the part left behind with another bit.  I just don't want to buy another bit to avoid the 10-minute pass with another bit to finish it off.

To make sizing the recess dead-nuts accurate, I'm going to use the KM-1 by Bridge City Toolworks.  The KM-1 works by using the size of your cutter (a router bit in this case) and the size of the dado (recess here) to create 2 offset fences that you'll see as I go along.

Set the 'orange' jaw of the KM-1 to the width of the bit your using.

Next, set the grey jaws of the KM-1 to the width of the walnut we're inlaying.  Keep it close by :)

Okay, this picture has several important points.  I swapped the stock base with the table widener.  In this case, I don't need the added stability the widener gives the OF-1400, but rather the added thickness that lets me use the guide stops off the back of the rail so the router is sitting on the stock instead of on the rail (I generally don't like it sitting on the rail since I never get the compensating support foot to lock solidly).  Note how I do not have the micro-adjusting screw of the guide stops attached between the stops.

Position the bit so it will cut the inside edge of the recess (inside meaning closest to the guide rail).

 I do use the dust guard, but find that I had much better visibility if I left the front part of the guard open.  It didn't change the dust collection much.  Remember that this is a down-spiral bit so most of the waste was left in the wake of the recess.

Measure from the guide rail to the inside edge of the recess as you'll use this to properly align the guide rail to the recess for all future cuts after the initial setup is completed.  Note that using a triangular bench rule like this one is nice since it butts up to the guide rail eliminating some error.

At this point, the router is ready to route the inside part of the recess, but we want this to be as "faster, easier, smarter" as can be so we need stop blocks calibrated with the KM-1.

In this picture, the leftmost guide block is first locked in place.  The KM-1 is placed between the guide blocks in the "long" position and the rightmost guide block is moved to touch it and locked into position.  The rightmost guide block will never be moved again in this project.  You'll notice something to the left of the leftmost guide block (apologize that it wasn't in the previous pictures).  That is the microadjuster for the MFK-700 as it fits perfectly on the rods and locks.  I use it as a well-sized stop block.  Butt it up against the left guide block and lock it in place.  You won't move it again.  Note that the "microadjust" ability is not used; it just sits there like a dumb brick marking a stop location; I plan on ordering another by digging through the Festool EKAT parts system.

Next, flip the KM-1 to use the "short" fence.  Loosen the leftmost guide block and move the router over until the KM-1's short fence is between the guide blocks.  I have a stop collar from a drill-bit set to the right of the leftmost guide block (right behind the KM-1... it's small).  It doesn't fit as well as I'd like, but worked.  Tighten this stop collar to mark the short fence location.  You can return your KM-1 to its hand-made walnut keeper chest now; the collars will mark our offsets.

This is where your router bit should be located right now after the adjustments using the KM-1 (if not, verify you didn't budge the guide rail).  Also remember that in my case, the tape is nearly identical width to my walnut; YMMV.

So now you are ready to crank through the routing operations.  Note in the original picture that several recesses line up within a French knot and to an adjoining French knot.  This is by design.  Even if your tape isn't perfectly laid out, using the guide rail aligned across all co-linear segments will make the whole that much better looking.

Here's the steps:

1. Place the guide rail the distance noted above from the inside edge of a recess to route.  Clamp the rail because patching this cork is not an option.
2. Loosen the leftmost guide block (one between stop collars) and slide the router until the guide block abuts against either stop collar.
3. Plunge and route; I usually scribbled with a red Sharpie at the ends of a segment so I could be forewarned when looking through the router window.  Stop early as it is easy to square the corner with a sharp chisel.
4. Loosen the leftmost guide block again and slide the router until the guide block abuts against the other stop collar.
5. Plunge and route.
6. Go to step 1 until you have no more recesses.  This is a very fast cycle.

Once the recesses are done, chuck up a straight bit (1/2" in my case) and freehand between the "moats" you just made to clear the waste between the edges.  This won't be neat.

Occasionally the rail didn't make it the whole way across the board.  It missed by inches.  For that, I inserted the rail connector into the rail and put a small piece of home-sawed veneer under the connector before clamping it down (veneer simply takes up the space under the connector so it doesn't pop the rail up).


Next up, cutting the walnut to length and mitered corners.  This isn't difficult, just tedious.  One tip: when 7 segments go in first-try and the eighth is being, uhm, fussy, check for new posts on your favorite forum.  Really, you just need to walk for a second.

So the rest of this has less to do with the router, but finishes the story of the floor.

Here's the walnut dry-fitted into the recesses.  You want a very snug fit, but try not to fully seat anything while dry-fitting since pulling it out can shred edges of the cork (this is why an up-spiral bit isn't appropriate).

 Paint the recesses with contact cement and let it flash off (about 30 minutes).

Paint the back of each inlay piece as well.  Note that I labeled each piece on the back to know where it goes.  Put pieces in order into the recesses.  I found that gently pushing them in and aligning the neighbors was the best way before pressing down hard.  Once you press down hard, it's done.  You'll want a scrap of cork glued to a block so you can use it to mallet the inlay pieces afterward to ensure they are seated and glued.

I used a shoulder plane to flush the walnut to the cork.  I preferred the medium shoulder plane mostly because the blade was just marginally wider than the walnut.  This greatly reduced the chances of striking the cork.




Voilà, the finished inlay!

For context, it will be in the entryway at the bottom of a set of stairs I refaced almost 2 years ago.  Here are some photos.

Bottom step will have the riser attached after the entryway is installed over the tiles you see to the right in the photo.

The landing has a French knot, as well.  It was done in a much more difficult manner; I was more stupid back then.  Oh, the lopped off corner of the entryway inlay is where the door is for the entryway so the entryway and landing will look the same from the top of the steps.  I have since installed base molding.

The bullnose of the existing treads was cut off and replaced with triple-beaded walnut.  Risers are home resawn lacewood veneer.  The corner molding you see here was custom cut and has continuous grain from the topmost step to the bottom.  Now, that molding is trivial, back then, it was tricky.  Guess I learned something :)