Saturday, November 05, 2011
Easy Shop-made Ellipse Drawing Jig
Popular Woodworking Magazine: Our December 2011 issue of Popular Woodworking Magazine features a gorgeous table project by designer/craftsman Jeff Miller. His Arch Table includes graceful, sweeping curves in the base. To generate the shape of these curves Jeff uses a shop made ellipse drawing jig. It's easy to make and crazy simple to use.
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There was an episode of This Old House where Tom Silva made an ellipse jig. It was different than this one and big more complicated. He used a framing square and two lengths to set his axis. I didn't quite understand. This seems very simple to make and was easy to understand how the geometry of the jig's 4 quadrants translated to the transitions of the ellipse. I kind of want to make one now.
Shop Made Jigs - 1 CNC 0
This looks like a pretty easy way to generate an ellipse. My great grandfather used to have a toy he made that moved in the same way, but I never realized that the end of the rod would move in an ellipse shape. Although it isn't necessarily the quickest guide ever to make, it certainly is the fastest one I've ever seen to make ellipses with. The only thing that seems difficult to me is relating the distance between the dowel points on the tracing arm to the final dimensions of the ellipse that gets drawn on your material.
Of the ways I know of to draw an ellipse, this has got to be the most practical of the methods. It does not involve some kind of annoying string rig or multiple complicated steps. This one seems to just take a few minutes to setup, and you could even use the same jig multiple times if you felt so compelled. What I really want to see is if this same setup can be used on a hand router. I can not think of a reason it should not be able to.
Ive always seen circle jigs made but have never seen an ellipse jig like this were you didn't have to find the foci. This seems like an easy and great way to make ellipses. You can always get a stock of different size 1x boards and use the same jig base which makes it a great way to use this jig for more than one ellipse. What would be nice to know is how to determine the size of the ellipse based on the dowel rod points.
i love little tricks of the trade such as these. the way you can make something out of nothing is one of the things that has always attracted me to carpentry. the work you can do and the way you make the tools you use to make the project is what really fascinates and excites me. this is the type of thing a machine can never replace , it requires the ingenuity and excitement of the human mind. the carpenter is a artisan who you can never truly replace and these little tricks are part of that.
This put a smile on my face. I always love it when stubborn problems can have such a simple and elegant solution. And the construction is so easy. Truthfully, I had to stop what I was doing for a few minutes to skecth exactly how this worked, the geometry more than anything else, and it was one of those Duoh! why didn't I ever think of that!? moments.
The ellipse template is a great time saver if you have to do a lot of them, but you can also make an ellipse with something even simpler - if you take two nails and a piece of non-stretchy string you can make an ellipse using no more than a pencil. Drive the nails partly into the surface at the two foci of the ellipse, tie the string in a loop around the nails so that if you pull the loop to a point it'll just reach the desired edge of the ellipse, and then if you hook a pencil into the loop and run it around the loop the pencil will travel in an ellipse.
The question I have is if you have a designated shape of ellipse, how do you translate that into the distance between the two dowels and between the dowels and the pencil.
With a circle jig of this sort, the creation of the jig makes sense, but in this I am not quite sure what is affected by the distance between the dowels. How flat the ellipse is?
However, if those numbers are easily manipulated, it seems like a very simple way to generate a complex shape.
I loved watching this video due to the clarity Jeff made while describing how to make and use this tool. This tool seems like one that would be of great use in any sort of shop. Once you make it you have it forever theoretically and you'll just change the size of your "stick" to specify the size of the ellipse you want to make. It also is an easy tool to use, and anyone who doesn't know how to use it can learn within seconds. I had never heard of making this kind of tool for yourself, but it is something I will keep in mind for the future if I ever need to make an immense amount o ellipses in a quick period of time.
So I am a big proponent of jigs in woodworking. I think they are as important as good tools and materials. I have seen people using similar ellipse jigs before: when you can get them to work, they work great. If, however, you don't know the math behind them you’re better off making and printing a 1-to-1 scale drawing. A jig is only as good as your understanding of how it works and how to use it. I feel like I could make the jig that Popular Woodworking shows in their video but I have no idea how to set it or how it works. It bugs me that they don't bother explaining how the two pegs correlate to the short radius and the long radius and that you can use them to make different ellipse shapes.
Yeah, this is great - I'm ALL FOR any method that doesn't involve CNCing a strange shape - but [and it pains me a little to speak ill, albeit indirectly, of Popular Woodworking] this method is ONLY good when you're making a table.
I don't see how this method, as good as it might be on a furniture scale, could be practical if you've got an ellipse 30' wide on its major access.
At best, this might work on something as big as a full sheet of 4x8 material but anything larger and I feel you'd start using more material for the jig than the actual piece. I've used the string method before and Charley's right: it sucks. But so far as I know, it's the only method that's scalable into something we, as stage technicians, can use.
I saw one of these set up at USITT last spring and it is a neat concept to cleanly create a difficult shape. Ellipses can be tricky, they seem like a simple shape but their creation, especially in drafting in studiocraft last year is very difficult and they generally look pretty terrible. There are so many things like this in all aspects of theatre that blow my mind when I see how someone has come up with a creative solution so solve a common problem, ever since the very early days when I saw someone make an large are with a pencil and some 1x.
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