elliptical mirror finally complete

[John Piwaron]

Some of you may remember my earlier posts about building David Marks elliptical mirror. I've finally completed it. While David's program Wood Works was helpful, in no way did I proceed the way he did. For one reason or the other I changed procedures to suit my expectations, skill and tool availability. So here goes:

First, I used Autocad to both figure out the ellipses I wanted and to see for myself that a router on a jig could cut it.

Next, I made a jig to guide my router giving me the elliptical templates directly.

I made 4 elliptical templates. One for the basic shape, one each for the mirror and the panel to hold it to the frame and one to make the second part of the two step rabbet on the back.

I also made 5 templates for the individual pieces that are mitered together and give the (very) rough ellipse. 3 of those templates are mirror image.

[John Piwaron]

The frame uses floating tenons. I made a jig to guide my router with a collar and cut the mortises. On Wood Works, David uses a multi router. A cool machine, no doubt, but far beyond my hobbiest budget.

I first test clamped and determined what clamp could go where. For this project, the number of clamps of these sizes doubled. That is, I only had 1/2 as many needed, so went to the store for more.

I used Gorilla Glue to put it together. I think yellow glue would have been plenty good enough, but my experience says that when I'm doing a complicated glue up, I'd better have a lot of open time in the adhesive or I might be in trouble.

When the glue had cured, I took that first template, taped it on with double stick and mounted up the big template bit and got to it. Then I routed the first rabbet and used another template to make the second rabbet. The mirror with a 1" bevel sits in the first rabbet and the plate to retain the mirror to the frame sits in the second. Then I rounded over the back outer edge with a 1/2" and flipped it over and rounded over the top inner and outer edge with a 1" radius.

These template routing, rabbeting and rounding over operations are the place I did things different from Mr. Marks. First, David says his frame is 1 1/2" thick. Well, the first frame I made (poplar) I did that and discovered that there is no land for the ball bearing guide to ride on. I ended up using a much smaller radius on the back outer edge to compensate. I also learned on the poplar frame that routing in the usual direction left a good amount of chipout on both the rabbet and the rounding over. All that chipout was unacceptable, but fortunately, I also learned that climb cutting is not so bad, especially with the huge heavy router I was using, my PC 7539. Especially with a big auxiliary base and some feet I had attached to it to straddle the frame while working on it. Those things provided lots of friction and stability to the router since the frame was so narrow. So when I made the "good" frame, I made it thicker for the bearings on the bits and I climb cut every inch of the way.

[John Piwaron]

So now we get to the fun part. I did the carving David did to his. Same tools and technique. A die grinder from Harbor Freight along with some carbide burrs (1" spherical and a big flame tip). My little pancake barely kept up. I used carving gouges to refine the shapes. This is one area where making two frames helped a LOT. I learned a great deal on the poplar that when I made the cherry frame it was darn near perfect.

[John Piwaron]

And the last is to say what I used. The first frame was poplar glued together with epoxy. I didn't like the line the epoxy left.

The frame you see is cherry. Finished with 5 coats of Waterlox and 2 of the Sam Maloof oil/wax mixture from Rockler.

The keyholes allow the frame to sit tight to the wall with no obvious method of attachment to give it away. I'm going to tell people that ask that it's held to the wall with magic.

I made 4 copy machine paper boxes of scraps through all this.

[Nancy Laird]

John, that is beautiful!!! I really like it.

Nancy

[Jim Becker]

Now, that's kewel, John!!!! Nice work!

[John Buzzurro]

John,

Beautiful job. Thanks for posting the detailed project description and pics.

[Mark Singer]

really nice work! The details and eecution are terrific!

[Larry Rasmussen]

Documentation like you provided is time consuming and I want to say the effort is really appreciated. Your description of process- the multiple templates, test piece and so on inspires me to slow down and try something challenging one of these days instead of dumbing down my designs to match my current skills. The finished mirror is just beautiful.
Larry R

[John Schreiber]

Nice design and nice work. It's so simple. But a close look shows how complex something which appears so simple really is.

[John Piwaron]

Thanks to all.

I tried to describe some of things I did differently from the Wood Works program.

I noticed while arranging the "keystones" that were the individual parts mitered to become the frame that they could slip past each other yielding a possilby a lot of different elliptical shapes. That's why I fixed the top and bottom in the approximate position I needed.

It was also a very good thing that I took David Marks advise and built two frames. I made so many mistakes on the first one, subtle mistakes, mistakes that make it look like a high school project, that I was very happy to have done it to learn from it. The one I've shown is the second one in cherry.

Yes, there was a lot of work to get to making the frame. Lots of templates, that jig and studying how to cut an ellipse without doing the string method Mr. Marks showed. He may be able to cut a perfect ellipse by sanding to a line, but I don't think I can. It was better for me to have used a jig.

I'm estimating the the support work was about 60% of the effort. The first frame taught me a lot of details. I'm guessing that if I were to make another one, it would take just 2 or 3 weeks.

Thanks again.

No project is beyond your reach if you break it down into it's tiny individual steps.

[Bruce Benjamin]

No project is beyond your reach if you break it down into it's tiny individual steps.


Ok, he said break it down into tiny individual steps...Now where is that extension cord in all of this mess! :o Nope, I have to start even start smaller than that.;)

Bruce

[Charles Bruno]

Nice job John!
I've wanted to make one the first time I saw it.
Looks good!

[Charles Jackson III]

Nice work, John!

[Don Bullock]

That's a great design and the final product is fantastic!! Thanks for sharing.

[Jeffrey Makiel]

It looks fabulous! Well done.
-Jeff :)

[Guy Germaine]

Very nice work. Would you mind elaborating a bit on the jig for the elipses? I've seen commercial versions at Rockler, but I figured it should be easy enough to make my own. Looks like you did!

[Rich Torino]

Real nice piece of work John... I like the detail..

[John Piwaron]

Very nice work. Would you mind elaborating a bit on the jig for the elipses? I've seen commercial versions at Rockler, but I figured it should be easy enough to make my own. Looks like you did!

It is easy. Figuring out the size of the ellipses I needed and the jig to cut them was the first order of business. FWIW, I think I spent about $30 building this. That doesn't include the polycarbonate router base which I already had lying around. Most of that money is for the Rockler T guide channel.

I saw an article in FWW that described what was needed to make a jig, I think it was entitled "cutting big curves" or somesuch.

Between that article and my own layout work, it took a pretty good amount of time. And through all this, the extensive amount of time I took building this was a matter of learing. Learning takes time.

I used Autocad to layout the ellipse and design my jig. Mostly, there's 2 centerpoints it pivots on. Each pivot point is actually a steel dowel pin pressed into a T shaped piece of hard maple about 6 inches long. That T rides in some of that aluminum track you can buy at Rockler. I had a machinist friend cut the ends of 4 pieces so they'd join tightly at the center. If you can't do that, there's a kit available with 4 small lengths that have that same kind of cut on the ends. I chose to make the cuts on longer pieces to avoid an extra 4 joints. I wanted to be sure the pivots would slide smooth and catch free. The base of the jig is 3/4" MDF. In addition to figuring out the sizes and relative positioning of my ellipses, it was critical to determine how the router base would pass over the jig base, determine where to to put the foot under the router base to hold up the unsupported end, and most critical of all, that the end mill I used would itself miss the base while cutting.

It is important to not that my particular jig will not cut every ellipse. If I get a yen to make another of different (narrower) shape, I'll have to figure out a different jig. But if I decide to cut an ellipse similar to this one, I can probaby reuse most of it.

The layout of the ellipse is pretty easy. The distance between the first two points that are always on the jig is 1/2 of the width of the desired ellipse. The distance from the outer pivot to the point of where the cutter is tangent to the ellipse is 1/2 of the long length of the elllipse. I made only 1 base, but two arms since the actual shape of the outer and inner ellipses are different. When I made the template that I used to cut the offset ellipse that would place the mirror retaining piece, I move the arm out by 1". This does NOT make a different shaped ellipse, it offsets the same ellipse by that amount. That fact was very useful.

Also, I found that my jigs repeatability wasn't really all that good, so the jig I cut the first time through was it. No resetting and going back for something I missed or screwed up. How'd I learn that? Well, on the template that I made for that offset ellipse, I tried resetting the jig to make another outside shape. I had planned to simply line up that template with the offset ellipse onto the outer ellipse after using the main template. Well, the second outside ellipse didn't match the first one.

So what I did while I still could was mark all the centerlines onto all templates and onto my work piece. So long as I kept things organized and worked deliberately enough to minimize brain farts, I was o.k. What I'm saying is that I lined up the offset template with the centerlines. And it wasn't super critical anyway since it only had to hold the mirror to the frame.

I used a 1/2" dia solid carbide spiral end mill to do the cutting.

And last, if all that is still confusing, I have an Autocad 2000i drawing of my layout if you want to study it to see what I mean.