ellipse jig - wow

[John Piwaron]

I learned something new today. The ellipse jig I built actually works. Imagine that.

I read the article in FWW about cutting big curves which included info on making an ellipse jig, in terms of the math behind it if not an actual plan.

So after drawing it in CAD and designing my own base and arm(s) for it, I built what I'd designed.

The fun part was that after I'd mounted my router, plunged the bit into the faux wood (MDF), it was almost effortless to guide the router around and get the ellipse. Wow.

[lou sansone]

hi john
how about a couple photos. what are you going to use it for ?

lou

[John Piwaron]

Here's a couple of pix. I hope.

The blue stuff are T tracks from Rockler. I did not use their bits that join them to cross at the center, I cut the end of each to a point so they'd form a cross. The Rockler parts would do the same, but that'd be 4 additional pieces and a lot of extra money.

The parts that slide in the track are made by me from hard maple and I pushed a steel dowel pin into a hole in the center. When I figured the geometry for each ellipse, I made two separate arms to go over those dowel pins. I got a toolmaker friend to make stop collars to go over those dowel pins securing the arms to the jig while still allowing the pins to rotate as needed in the hole. The portion of the arm the router attaches to is adjustable to the arm, so I only made 1. I have the centers marked so I can measure the lengths when I set it up for a particular ellipse. The router is a PC 7539.

The base of the jig is attached to the material below it with 4 screws.

When I cut the ellipse with the jig, I didn't go all the way through the mdf so I wouldn't hit the surface I had it laying on. I routed most of the way through, then I cut the template away from the sheet and cleaned it up with a pattern bit in a router.

The last picture is the completed ellipse. I'm using it as a template.

What this all about is to make the elliptical mirror David Marks made in an episode of Wood Works. David doesn't give much in the way of specifics to replicate what he makes in some of his shows. That wasn't going to stop me.

Mine will be cherry, not bubinga. Not 'cause I don't like bubinga, but because I feel cherry will look better in my house.

[Dennis Peacock]

Hey now....that's a nice jig setup. Congrats on your accomplishment.