Routing a juice groove in an oval cutting board

[Mel Fulks]

Keith, you might well be able to hold the router exactly oriented. I've seen some attempts that were failures. It's a lot easier to do a circle like that than an ellipse. What I suggested requires one plywood template with one edge, elliptical casings routinely
need two edges and one of them has to be scribed from the other as the jigs will not make two equidistant edges.

[Eduard Nemirovsky]

If you already create outside edge, why not use an edge guide with your router, something like this - https://www.youtube.com/watch?v=QHQxPkIVfT4. Check about 1 minute in the video.
Ed.

[Roger Feeley]

what if you cut a template in the negative. An eliptical hole in a larger piece of wood that is 1/4" larger in all dimensions than the desired size. Using a core box router bit and a very large bearing, cut the groove first. Then, using a 1/4" pattern bit, plunge right next to the template and cute the board out of the larger piece. You are using one reference template with no alignment change. I wouldn't cut all the way through on that last step. Leave a 16th of in inch holding it together and saw it apart. A little sanding and then a roundover bit would clear away the flash.

Cutting the part away would be the tricky part of this. If the router moves away from the template, it's eating the part you want, not the waste.

Can you get bearings that big? Hmmm... I just googled it and Infinity has a set. https://www.infinitytools.com/routing/router-arbors-bearings/16-pc-ultimate-router-bit-bearing-kit
They have cheaper sets. Just noodle around.

So my suggestion is not to cut the oval and then try to cut the groove. That's hard. My suggestion is to cut the groove and then cut the oval. The key is to use a single reference for both operations.

[Andrew Gibson]

I like using an edge guide with a couple dowels glued to it.
img_0342.jpg

[keith micinski]

Most guides have the cutout in the middle positioned in such a way that the two inside edges do the same function as the dowel pins do, I forgot to mention that in my post but the dowel pins is a much more secure way to do it and a really good idea.

[Dan Hahr]

I ended up going with a temporary edge guide attached to the base. I cut a curved edge with two points to act as dowels. I had to space them relatively close, 1.5 inches apart, so that the distance from the groove to edge didn’t change noticeably around the different curves. I used a full size router and had to have my son turn it for me as I went around it so I could always keep pressure on both points. It worked very well as I took light cuts and made several passes. Thanks for all the suggestions.
Dan