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Thread: How to make a oval template?

  1. #16
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    Word of caution here. The use of two opposing parabolas will get you into trouble. Dale is right. That is not the usual formula for an ellipse... rather, its something I used years ago doing some layout. Dont even wish to go there on a woodworking forum.

    A circle is a special case of ellipse in which both centers are conincidental.

    But who needs to remember all these goofy equations when you can just setup the micro fence. Using a micro fence makes this task brain dead and what the micro fence does not kill in terms of brain cells, jack daniels does the rest.
    Had the dog not stopped to go to the bathroom, he would have caught the rabbit.

  2. #17
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    Hmmm?

    Quote Originally Posted by tod evans
    this method is far more accurate than the string method...tod
    tod,
    You may be right but the "string method" is an EXACT replication of the mathematical equation that defines an ellipse! I'm not sure how you can get more "accurate" than that?

    Tell me where I am wrong.

    Dale T.
    I am so busy REMAKING my projects that I don't have time to make them the FIRST time!

  3. #18
    dale, using the string method there is to much human error involved. when the points are mounted solidly to a trammell the chance for human error is greatly reduced...02 tod

  4. #19

    Oh, I got this one for sure!

    Simple Just go to mirror store and pick out an oval mirror. Trace the mirror onto your project wood and then "carefully" cut it out. Now, make everything else fit around your table top. Geez, this one was easy.

    David "just having fun" Pettibone

  5. #20
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    Gee Whiz!

    Quote Originally Posted by tod evans
    dale, using the string method there is to much human error involved. when the points are mounted solidly to a trammell the chance for human error is greatly reduced...02 tod
    tod,
    From what I can gather, the "Trammell Method" requires several "human" measurements. The "String Method" requires only one. A simple "Pothagorean Theorem" calculation and a single measurement of a "string" length and it's all over.

    As a totally stupid example, what if the ellipse requirement was for an ellipse with a major axis of 100 yards and the minor axis was 40 yards? With the "string" method, it would be quite simple and very accurate.

    Dale T.
    I am so busy REMAKING my projects that I don't have time to make them the FIRST time!

  6. #21
    dale, you are correct, if i could hold the pencil to the string accurately and if the string didn`t stretch or ride up on the nails then the string method would be extremely accurate but to date i haven`t been able to coordinate myself well enough to get acceptable results using this method. so when i must layout a geometrically correct ellipse (2-3 per month) i`m forced to use the trammell method. in fact i`m currently addapting one of the industrial picture matting cutters to hold a router. this machine uses thompson linear bearings on the x&y axises so as to eliminate the human error i encounter when trying to describe a perfect ellipse. maybe it`s only me who has problems getting an accurate repeatable line using a string but i am working on a solution tod

  7. #22
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    Why didn't you TELL me?

    Quote Originally Posted by tod evans
    this machine uses thompson linear bearings on the x&y axises so as to eliminate the human error i encounter when trying to describe a perfect ellipse. tod
    Tod,
    How could I EVER argue with a machine that uses a THOMPSON component as part of its operation. EVERYTHING that you do must be PERFECT!

    If you are wealthy enough to afford THOMPSON components, you can easily use the string method. Just get a THOMPSON rubber band for your string, a couple of THOMPSON ultra-light flex poles for your points and a plugged up can of THOMPSON spray paint for your lines. Believe me, you will redefine the word "ellipse".

    Tod, as is often the case, it is works DON'T fix it!!

    Seriously, though, those Thompson linear bearings are really the cat's meow. I invented them just for you!

    Dale T.
    I am so busy REMAKING my projects that I don't have time to make them the FIRST time!

  8. #23
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    Quote Originally Posted by Alex Berkovsky
    In the future, I'll be making this simple jig.
    I downloaded the plans and will probably build one. Just wondering if it can very narrow and wide ellipses? Like for a cutout at the base of a kitchen cabinet?

    I just did one by hand with a string for a bench I am building and its not right. Not sure what happened but I am going to have to redo it.

  9. #24
    jeff, try the simple trammell i discribed earlier, you`ll be impressed....02 tod

  10. #25
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    Todd, I was a draftsman/mechanical designer in my prevous life. Used to do that stuff all the time. Problem is I don't have a set of trammel points and my old compass(es) just isn't big enough for this. Watching for a set but they keep going higher than I want to pay. Otherwise I would do (and will) do it that way.

    Just got to find a decent set at reasonable price

  11. #26
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    For the LITTLE guys like me!

    Quote Originally Posted by Jeff Horton
    I downloaded the plans and will probably build one. Just wondering if it can very narrow and wide ellipses? Like for a cutout at the base of a kitchen cabinet?

    I just did one by hand with a string for a bench I am building and its not right. Not sure what happened but I am going to have to redo it.

    Jeff,
    For the folks who make elliptically shaped parts on a frequent basis, the jig referenced in a previous post can be ideal. These jigs, however, are limited in terms of the size of ellipse that they can make. The jig shown could not make an 8"x10" Ellipse for a jewelry box or a figurine stand. Also, it would have a hard time with a 6'x18' Elliptical bar deck "island" or whatever. Making a jig for each of these could prove to be both time and space consuming.

    Most hobbyists do not make a lot of ellipses. In addition, our shops are not large enough to store all of the handy jigs that are used by the pros. That is why I am a proponent of the "little" guy, the poor, the homeless, the oppressed, stray kittens, motherhood, apple pie, the space-challenged and the amateur. (I don't need any wise remarks about stepping on my cape! ). OK - Go ahead!!

    Anyway, I'm taking one more shot even though I will be repeating some of the information provided by previous posters.

    ALL ellipses are ovals! All ovals are NOT ellipses. Mr. Stuard appeared to use these terms interchangeably in his fine referenced article. For example, an egg is an oval. It is, however, NOT an ellipse! I also disagree with his statement that the "String Method" is "sloppy". Woodworkers are NEVER "sloppy" except, AHEM, for maybe one. With that said, I don't ever recall him visiting MY shop and watching me slobber wood filler in every miter, dovetail and other "creative" joint that I come up with!

    There are several math approaches to the brad locations for an ellipse. I'm sort of a minimum BS person so let's try this:

    Let's say that you want to make an ellipse that is 56"x24". 56" will be your long dimension and 24" will be your short dimension. From this we already know that our "string" will be 56" long! Half of the problem is already solved!

    However, we still have to locate the distance between our two brads. That's not too bad so let's take a shot: Cut both of your ellipse dimensions in half and you will get 28" and 12". Next: Add the 28" to the 12" and get 40". Now subtract the 12" from the 28" to get 16".

    Multiply the 40" times the 16" to get 640 square inches. Now take the square root of 640 square inches to get 25.3".

    You now double this number to get 50.6". That is the spacing of your brads, spikes, telephone poles, etc. PROBLEM SOLVED!!

    For the above 56" by 24" ellipse, your brad spacing will be 50.6" and the "string" will be 56" long.

    I hope that you are not as confused as I am?

    Please PM me with your dimensions if I can be of any further hindrance.

    Dale T.
    I am so busy REMAKING my projects that I don't have time to make them the FIRST time!

  12. #27
    David Marks method when he made the oval (or elliptical ?)mirror. with pictures so it's easier to understand


    http://www.diynetwork.com/diy/ww_dec...277964,00.html

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