As usual, click any photo to bring up a larger version.
I have to give lots of credit to Reddit user "joelav", as I learned a lot from his imgur photo gallery. Here is the link: http://imgur.com/a/FnIq4
(As a side note, I find that what to call this type of cutting board is a challenge. It's not really an inlay, since an inlay doesn't go all the way through a piece. But I've called it a curved inlay myself. I'm going to go with "curved insert".)
Note that you cannot just cut a curve in the cutting board and then slip in a curved strip. If you do that, it will distort the look of the board -- the straight boards that make up the board will be offset on either side of the curve, and appear broken. Instead, we need to remove a curved section of the cutting board, that we will then replace with a curve of identical width.
For this next pattern I turned to a set of french curves to help with coming up with a pleasing and fair curve. (A "fair curve" is a boatbuilding term having to do with a smooth curve without extraneous bumps or hollows.)
An important side note here is that the pattern should be at least a few inches LONGER than your cutting board. This gives you more freedom with positioning and/or angling the pattern to lay out how the curve flows through your board.
This operation is critical. The thickness of your router bit is what determines the thickness of the strip that you will be fitting into the cutting board. In my case, I used a 3/8" straight bit, so I need to fit in a 3/8" replacement curve strip. I also need a guide collar on my router, which rides tight along the pattern that I made.
I used two passes of the router to cut about halfway through the thickness of the board.
NOTE:A few people have asked why I don't cut all the way through the board with the router. The short answer is that this is the way I learned, and so that is the method I follow. But also, If you were to route all the way through the board you would need a way to firmly support and clamp both sides of the cutting board so that so that one side does not shift during the cut. And so that one side does not break off partway through the cut. And so that the one side does not fall to the floor (and be damaged) AFTER the cut. And also that there is router bit clearance UNDER the piece while still being firmly held and supported.
It probably is possible, but I think this way may be simpler.
Oh, and in the left side of the photo you can see my pushstick for thin stock. It rides over the fence, and my hand gets nowhere near the blade. This shot is from just before I picked up the pushblock (a screen capture from the video).
I applied a generous helping of Titebond-III glue to the strips and to the cutting board and then clamped them together to dry. If you have them, quick-grip clamps are very helpful in this operation, as the trigger-operated squeezing action makes it a lot easier to bring the two sides together. You need to close up a fairly large opening.
Another thing to watch out for here is slippage. I did my best to ensure that the two sides of the board stayed flat. However, I also had anticipated needing to plane it afterwards, so I had a little bit of extra thickness to play with.
And after that I ran it through my planer for a few light passes to finish up flattening both sides.
I now had one curved insert strip installed in my cutting board. If I wanted another one, to make a double-curve board, as I did with my prototype, I would go back and repeat the whole procedure. You can use the same router curve template pattern, just flip it around and use the other side.
I decided to stop at just one curve this time.
I just use a clean rag and work the mix into the wood and buff it well.
Here are my two boards. On the right is my "prototype". It is made up of strips of Cherry and Hard Maple. There are two curved inserts, made up of three strips of Walnut and two of Padauk. On the left is my second board, documented in this build. It is made up of strips of Cherry and Walnut. It's curved insert strip is made of three strips of Maple, and two of Redheart.
A few more photos follow, showing different views of the boards and process.
Next two photos are of the second insert strip being glued into place.
Thanks for reading!