Optical Illusion

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Remember that you can enlarge these photos by clicking on the actual picture.

I’ve been looking at the Egerton clock for sometime. What’s cool about this clock, if I haven’t wrote about this as of yet, is that the scroll-board is pierced so the sound of the bell strike is better heard. As I work on the hood, it’s time to make decisions about the pattern work in the scroll-board.

I should also add that the pattern of the scroll-board is cut into a piece of veneer and that veneer is placed over holes drilled in a scroll-board backer. A piece of dark cloth is fitted between the two in the original clock.

Take a look at the photo. Can you see a pattern. I thought I had it a couple times, but when I set down to  plan the layout, it never came together. At first, I was trying to look at and figure out the dark areas, the areas I needed to remove. It just didn’t work.

LayoutFinally, I decided to look at and study the non-dark areas, or the material that stayed in place. I know there are brain-teasers that make your mind work to see the opposite, but I never figured thought this would be an example.

Once I changed my point of view, I figured out the pattern. Just above is a SketchUp drawing of my latest rendition. In it I have lines set at 45 degrees and spaced every 5/8″. The small circles are 1/2″-diameter in size. At each crossing of the layout lines, I put a circle. Next I connected lines between the circles. each line is space an 1/8″ apart.

In SketchUp, when you connect or close areas they change color. I went back and removed any colored section from the circles and areas between the connection lines. That left the waste areas dark, just as in the scroll-board. Below is a close-up look at the layout.


Yes, I know there are a couple lines missing.

All I need to do now is complete the circles – if I want or need to see the completed layout. Or with the 45-degree lines in place, I know that the centers of my circles fits at each intersection. Of course, I also need to chop out the waste which I believe will be done using a combination of carving gouges sized to match the circle circumference and chisels. Unless you guys come up with a better idea. Help.

Build Something Great!




Filed under Tall Clock

4 responses to “Optical Illusion

  1. Charlie

    Glen, I looked over the photo and to me the holes look fairly square. I think that I’d use a Mortising machine to cut them out. The center of the circles you could drill with a small drill bit. 1/16″ ? or perhaps a brad point drill bit, only deep enough that it would leave a center hole and a scribbed circle. Follow me ? It would sure save you alot of time and still look good.

  2. Charlie

    Scrap the brad point drill bit idea, on plywood or veneer that may not work out so good. Possibly too much chiping.

  3. Charles Wilson

    If the veneer isn’t too thick, you might be able to make a metal cutter to slice out the openings. A Bent razor blade might be a place to start.

  4. Daniel Feeser

    With almost a thousand individual cuts to make I think you should look at how the operation can be mechanized. Or, do you just have way too much time on your hands??

    Options I think are possible:

    Create a two edged comb consisting of dados of the width of the gouge at the required spacing. Two edged so you get more cuts for each positioning of the comb. This would allow you to get the spacing correct and give you a edge to register the gouge against for the alignment of the cut. Still tedious because of the number of times you need to position the comb to get all the curved segments, first horizontally then vertically.

    Shape the cutting edge of a hollow chisel from your mortise machine to match the cutout. You may need to build up the end of the chisel to allow enough material for machining. Thinking about this more, a drill press based mortising system may be better because of the reach it would allow.

    As Managing Editor I am sure you can get an article on laser etching and cutting machines incorporated into a future edition of PW. I am sure there are a number of companies that will loan (better yet – maybe donate) machines for the article. With machine in hand it should be a piece of cake to program the machine to do all the work. As long as the control system is more sophisticated than an “Etch-a-Sketch” you should get a great product.

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