I have a student that designed a coffee table with an elliptical table top. The ellipse is 36″ long and 14″ wide. The large length-to-width ratio proved to be impossible to create with the typical crossed slots and trammel type ellipse jig. The student was able to use AutoCAD and plot out the full sized pattern. But trying to cut it out accurately with a hand-held jig saw in 1″ thick hard maple didn’t yield useable results (the blade wouldn’t track vertically).
I thought I could invert the typical jig strategy to make a guide I could clamp to the bandsaw table which would pass her board on an elliptical path through the blade. The guide worked fine, but the ellipse does not remain tangental to the blade kerf, and as such binds the blade within a few inches of the cut. It became clear that I could use the guide on a router table to cut the ellipse, but in the student’s case the router bit would remove too much of a path. The student wants to use both the interior ellipse and the remainder of the rectangle in her design, fitting them back together with only a minor gap in one tranformation during use. We’ve now found someone local with a high-pressure water pattern cutter that can use her ACAD drawing to cut the pattern from her 1″ thick rectangular maple blank.
In experimenting with my new ellipse jig, though, I discovered it can be used to make very extreme ellipses. I’m making an elliptical plant stand, for example. The top is a golden-ratio ellipse approx. 14″ x 22.5″. It is supported by crossing rectangular/tapered panels that have ellipses cut from the center, and half-ellipses cut from the bottom edge to create feet. I was able to accurately cut 22.25″ x 10″ and 22.25″ x 4.75″ full ellipses from the center of the panels, and 11″ x 6″ and 4.125″ x 6″ half ellipses from the bottom edges. With my jig all panels were passed on an elliptical path through a 1/2″ straight bit on my router table. The bit was raised in 1/4″ increments for each pass, with the last pass cutting through and releasing the interior ellipse from the exterior panel.
If anyone is interested, I’d be happy to write a full article on the jig, and the process of creating this particular table with it. When the table is done I’ll try and post a picture in the gallery. IF you’ve every needed an extreme elliptical part or hole, this is a sure way to create them.
If there are any clever jig makers/engineers out there, I’m still interested in a jig that will pass a board on an elliptical path tangentally through a bandsaw blade. Any ideas?
4DThinker (Dave Brown, professor at Kansas State University, Interior Architecture Dept.)
Edited 10/16/2003 4:50:48 PM ET by 4DTHINKER