Cutting a Bigger, Better Ellipse
posted on September 13, 2007 by Rockler

image of rockler ellipse jig Getting tired of building boxes? Aren’t there a few other shapes that a woodworker can make? Of course, there’s a reason why 90 and 45 degree angles are so popular with woodworkers: We know how to make them, and our favorite tools do, too. An elliptical frame or coffee might make a refreshing and challenging departure from same old rectangles and squares. But the question is, how do you turn a piece of wood into a nice, smooth, mathematically correct shape that isn't made up of straight lines?

Maybe you’ve tried the old “two thumbtacks and a piece of string” method. You know the one: Tie a piece of string into a loop and use it along with two tacks positioned at the foci of the ellipse as a guide for tracing the shape. Most would agree, though, that this works better in theory than in practice. If you’re not handy with algebra, getting the tacks in the right place and the string tied into the right sized loop is nothing more than time-consuming guesswork. And when you do get the shape drawn out, what do you have? A drawn-out shape. You still have to cut it, and that usually means freehand, with a jigsaw or band saw – and then sand, rasp, plane or whatever until (hopefully) it turns into a smooth, fair-curved ellipse.


Fortunately, there’s a much better way: With an “ellipse jig” and a router you can define and cut an elliptical shape in one fell swoop. An ellipse jig (sometimes called a double trammel jig) isn’t new technology by any means. It’s essentially a big compass that uses two sliding pivot points to guide a router along the perimeter of the ellipse. You’ll find plans for constructing, and tips on using this time-honored router accessory in most router technique books.

Making your own ellipse jig is a viable option, but it’s a little more work than most folks want to spend setting up for a project. There’s a fair amount to an ellipse jig. You need a trammel arm that can be attached to your router, a jig base with two very accurately cut channels to guide the two moving pivots, the two moving pivots themselves, and some way of attaching them to the trammel arm. In other words, making an ellipse jig that works well the first time, and will last through several projects, can eat up a fair chunk of shop time.

And why bother, when you can just send out for the Rockler Ellipse Jig? It’s an affordable piece of equipment, and it’s all set to go. It’s even predrilled for porter cable 690/890 series routers. You don’t need to know (or do) any math, you don’t have to pre-draw the ellipse, you don’t really even have to understand how the jig works – the instructions are printed right on the jig, and walk you through the entire process one step at a time. All you really need to know is how to use a router, and how big of an ellipse you want to make. And you’ll have a lot of range there if you also pick up the new Large Ellipse Base. This new add-on base greatly expands the range of larger ellipse proportions the jig can handle, increasing the maximum difference between the length and width of the ellipse from 8” to 14”. 

All of the jig’s moving parts are precision machined from tough phenolic resin – an aspect that would be hard to replicate in a shop. The phenolic material slides easily, so you can concentrate on keeping the router moving at the appropriate speed. And it won’t wear out, even if you take after ellipse-making with a vengeance. And once you see a couple of near-mathematically perfect ellipses appear quickly, easily and almost magically before your eyes, you may decide to do just that.

posted on September 13, 2007 by Rockler
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Comments

9 thoughts on “Cutting a Bigger, Better Ellipse”

  • I used the jig for the first time yesterday, and I was impressed! I'm making three oval frames for family members. Once I had the measurement for the outside edge of the frame, it was a matter of cutting that and then moving the jig in 1.5" on each axis. <br /><br />Mind your cords to avoid any contact or tangling. And make cuts in small increments.<br /><br />The jig is a worthy investment!

  • Blog Editor

    Thanks for the comments and the tips. Rigging up a simple cord hanger above the work helps with the cord problem. <br /><br />Good advice on making the cut in several passes. Once the jig is set up, it will follow the exact same contour for as many revolutions as you want. Making several passes to complete the cut incrementally will almost always yield a smoother finished product.

  • Just wondering what the max. dia. you would be able to cut.<br />Does the base come the rockler ellipse or that purchased separate?

  • Blog Editor

    The max diameter with the large base is the same as with the smaller base: 52". The difference with the larger base is that you are able to set the sliders farther apart. The effect is a greater possible difference between the length and the width of the finished ellipse - up to 14" more with the large base. The benefit is more range of proportions for larger shapes.<br /><br />The jig arm does not come with the large base. Right now, it only comes with the standard <a href="http://www.rockler.com/product.cfm?Offerings_ID=17282" rel="nofollow">ellipse jig</a>.

  • John

    Yes, this is a very old concept. If my memory serves me Fine Woodworking # 56 had an article about a place near Boston that had German lathes dating back to around 1850 that they turned oval picture frames on. Also you can find a related version of this in gift stores called a BS grinder or Idiot Box where you crank the handle and the 2 pieces slide back and forth. I developed my own version to draw ovals, I make 15x20 rectangular mirror frames with an oval center for the mirror. I have just purchased a new Freud Quadra-cut router bit to shape the edges and really make a smooth cut.

  • Blog Editor

    Thanks for the comments. And you're right, there's nothing new about the concept. We hope the jig makes putting it into practice easy and cost/time- effective, though. <br /><br />Oval turning, as you mention, has been around for a long time. For anyone interested in learning more: you'll find a wealth of information on turner <a href="http://www.volmer---ovaldrehen.de/englisch.htm" target="_blank" rel="nofollow">Johannes Volmer's website</a>. <br><br>Also - glad to hear, again, that <a href="http://www.rockler.com/blog/index.cfm?commentID=270" rel="nofollow">Freud's Quadra-Cut</a> bits are living up to their reputation.

  • dave wingfield
    dave wingfield April 9, 2011 at 7:12 am

    how small of ellipse can be made with the jig (for small picture frames)?

  • Rockler Blog Team
    Rockler Blog Team April 11, 2011 at 10:12 am

    Dave - Thanks for the question. The smallest ellipse that can be made with the standard ellipse jig (http://www.rockler.com/product.cfm?page=17282) is 9-1/2" for the minor axis and 17-1/2" for the major axis. We also have a set of small oval templates (http://www.rockler.com/product.cfm?page=21285). Maybe they would be better for your purposes?

  • Jerry

    purchased a ellipse/cirlcle jig a few years a go did not use until now but I see that all parts are not with the jig is ther a way to pushcase the missing parts

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