I have seen a few examples online of cutting boards with curved inserts such as this. I've wanted to make one myself for a while, and so I finally did. My prototype is shown here. I then made another one and documented the process. I have to give lots of credit to Reddit user "joelav", as I learned a lot from his imgur photo gallery.
Step 1: Option: Video Build
If you would prefer, you can watch a video of this project build. Otherwise, read on!
Step 2: Where It Begins
This project starts where another might end. Here is an almost completed cutting board blank. A bit more work -- rounding the corners, adding a finger hole -- and it would be read for finishing. But this is where I start on this project.
The goal is to add a curved insert to the board, made up of several thin strips of contrasting wood.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.
Step 3: Make a Router Template
The curve is made with a router template such as this piece of MDF.
For this 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.)
Over on the bandsaw I cut out the pattern, trying to stay as close to the line as possible.
The pattern was then refined on the disc sander (outside curve) and spindle sander (inside curve). But it still needed a bit of hand sanding to finish it off. I glued a piece of sandpaper to a long thin piece of wood. This gave me a long springy sanding stick that would follow the major curve and helped with sanding down the few bumps.
Step 4: Make the Curve - Part One
The next step is to layout the pattern on the cutting board. This is all a matter of taste -- here is where you can get creative with how you want the curve to flow through the cutting board.
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.
I hope you kept the cutoff from making the curved pattern. I use it there to support the one side of the router, to make sure that the router does not tip during the cut.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.
Step 5: Make the Curve - Part Two
I then split the board in half, cutting down the center of the curve. I'm not trying to get close to either side, just go down the middle.
Then it is over to the router table. I put a pattern routing bit in there, and I set the depth so that the bearing rides along the nice curve that was cut with the pattern. In this way the bottom of the curve is cleaned up and we're left with a nice clean curve.
Step 6: Make the Insert
Over on the tablesaw I cut some thin pieces of hard maple, and Redheart (Chakte Kok) for my insert strip. 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.
I need a 3/8" strip to go into my cutting board, which is 0.375 inches. Using my calipers I see that I have .395 inches, which is pretty close. I did lightly sand each strip, mostly just to clean up the saw marks, but that would also bring it just a touch closer to my ideal thickness.
Step 7: Insert the Curved Insert
And now the fun begins...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.
My strips were a fair bit thicker than the cutting board, so after the glue was dry, I took the cutting board over to the bench and planed them down so they were close to flush. After that I ran it through my planer for a few light passes to finish up flattening both sides.
I then brought it to the tablesaw to square up both ends.
Step 8: Do It Again?
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, or shift it around somewhat to vary the second curve.
I decided to stop at just one curve this time.
However, here are some photos of the process of making my other cutting board where I did glue in a second curved strip.
Step 9: Final Steps
I drew and cut curves to round-off the corners, and marked and drilled a finger hole. Finally, I used a 1/4" roundover bit in the router to round over all the sides of the cutting board. After that I sanded it smooth.
I like to use a salad bowl finish for cutting boards. It is available from Lee Valley Tools and is nothing but a mixture of mineral oil and beeswax. It is totally food safe. In fact, you can start using the board as soon as you wipe it on. I just use a clean rag and work the mix into the wood and buff it well.
Step 10: Glamour Shots
Some Photos of my two Cutting Boards