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How to build an oval cutting jig (elliptical router jig)

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Blog entry by BenhamDesign posted 12-06-2018 07:46 PM 666 reads 3 times favorited 4 comments Add to Favorites Watch

I got a wild idea to build an oval table and I didn’t want to wait for a store bought jig to show up in the mail, so I decided to make my own.

If you are interested you can watch it on Youtube or read about it below

Video recap
Today I’m making a shop made oval cutting jig, because I needed it to build this table. That video should be out in a few hours, so please check back

I started out the build by cutting the base to size. I’m making it out of ¾” plywood but ¼” would be better, I just didn’t have any on hand that wasn’t shaped like a potato chip,
Once the base was cut I started milling up some scrape maple for the runners

I jointed one edge and ripped of the other making both edges square. I tilted the blade to 10ish degrees, the exact angle isn’t important.
I thin ripped off a slice from each side; these will be my edge guide pieces
Then I ripped off a third piece with the beveled edge against the fence, creating a trapezoid shaped. This will be my runners.
I cut 2 small sections off the trapezoid piece. These will be the pivot points in the jig.
I rounded over the ends at the spindle sander so the edges wouldn’t get hung up on anything.

Then it was time to cut the edge guides to size. I mitered one end then cut the other end to length.

Back at the base piece I had cut earlier, I drew a few center lines to work from; I installed the first edge guide with some CA glue. I took extra care to be sure that the 1st 2 pieces were square.

Then I used the leftover length of the trapezoid piece as a spacer to install the other edge guides.
Before gluing in place I made sure the trapezoid piece slid freely but with minimal side to side slop.

I just worked my way around the jig, until I had all the pieces installed, any glue squeeze out I cleaned up with a chisel.
Once I had all the edge guides installed I eyeballed the center of the edge guides and transferred those lines down the bottom of the base.
I counter sunk for some screws and added a few screws for strength. I just don’t trust the CA glue bond against the strength of a runaway router.
On my runners to create the pivot point I found the center and drill a hole for a ¼” bolt to pass through.

I traced the shape of the head of the bolt on the bottom of the runner and chiseled it out so the head of the bolt was below the surface.

Now to make the swing arm I ripped a piece of plywood to size and made sure both ends where square.
I drew down a center line, and then marked of every inch.
I headed to the drill press and drilled them all out so the ¼” bolt can pass through them.

I did a little test run to be sure everything was running smoothly. I think after adding a little past wax I will work perfectly.
Now to be sure the router won’t hit the corners of the jig I clipped off each corner at 45°

I will have a set of plans on my website that will call out a ¼” for the base instead of ¾” so you won’t have to do this next step since a standard base on a router is about a ¼”

To make up the difference in thickness I cut out a thicker base plate of ¾”plywood to screw to the router.
I just traced the base place from the router and transferred the holes for the screws. Counter sunk them at the drill press and cut out the circle at the band saw.

Now to attach the jig to the router.
I measured the centers on the router where the edge guide usually attaches to. Transferred those measurements to a piece of plywood drilled for the bolts to go through and used a forstner bit to counter sink for the bolt heads.
Here is where I screwed up. I should have assembled the jig as I had it built before taking that measurement. The edge guides of the jig create an offset so I actually needed a wider piece.
But let’s carry on like nothing happened.
I cut that piece to the wrong width.
Then pre drilled for some screws.
Attached it to the swing arm
Clamped one side to hold it to the router while I pre drilled and screwed the 2 pieces together.
Here is the basic gest of how it goes together. The holes on the swing arm are an inch apart and the bolts that attach the jig to the router are longer than an inch long.
Those bolts give you the flexibility to adjust the width and length, exactly to you want your oval to be.

Thanks Brian

-- What I do in and out of the shop at http://www.BriansBenham.com



4 comments so far

View Andybb's profile

Andybb

1506 posts in 805 days


#1 posted 12-06-2018 08:06 PM

Nice job! Favorited. I know I will need it someday. Thanks.

-- Andy - Seattle USA

View BenhamDesign's profile

BenhamDesign

169 posts in 1622 days


#2 posted 12-06-2018 08:21 PM



Nice job! Favorited. I know I will need it someday. Thanks.

- Andybb


Awesome thanks

-- What I do in and out of the shop at http://www.BriansBenham.com

View Andybb's profile

Andybb

1506 posts in 805 days


#3 posted 12-06-2018 10:07 PM

Oooo. And I like the oval table and sculpted legs. A fence on the miter saw would keep that chunk from getting sucked up in there. :-)

-- Andy - Seattle USA

View splintergroup's profile

splintergroup

2429 posts in 1424 days


#4 posted 12-06-2018 10:11 PM

I can’t count how many times I’ve needed to do this and have been too lazy to build a decent jig. “I’ll never use it again”

It’s good to have information like this handy, thanks!

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