How to make a oval template?

[Larry Crim]

OK I saw it here somewhere but can't seem to find it now but I am thinking of making a oval top for my coffee table and was trying to figure out how to make the oval, I assume you would make a template them cut the scrap away and then route to finish. ? is how to make the oval template, I remember a post where they used a string and two posts but can't find it. Any suggestions?
Thanks
Larry

[tod evans]

larry, to lay out an ellipse draw two lines 90deg to one another mark the distance from the point where the lines cross 1/2 of your measurement on each axis, one large(major),the other small(minor). using a trammell set the points to 1/2 your major axis,or from center to previously made mark.place one trammell point on the semi-minor axis, the short mark, and bisect the line of the major axis twice, once on each side of center. using the two points you have just described (x`s slightly in from the semi-major axis mark) drive a nail, also drive a nail at one semi-minor axis( short side mark) wrap a string around the three nails and tie it together then remove the nail at the semi-minor axis and replace it with a pencil and describe your ellipse. much easier to do than describe in print! tod

[Larry Crim]

I had to read it about 5 times but I think I understand now
Thanks
Larry

[tod evans]

sorry man i`ve been spraying lacquer since 5am, my typing may be even less than my normal substandard affair....but i`m having fun:) tod

[Alex Berkovsky]

Larry,
See if this site (http://personal.atl.bellsouth.net/e/d/edwin222/ellipsefoci.htm) helps you understand what Tod explained.

[Dev Emch]

The problem with an oval is that its a circle with two centers or an ellipse in which you have two back to back parabolas with dual opposing foci. In some cases, its hard to tell the difference. In other cases, the ends are more football shaped.

In either case, this exercise presents some frustration to folks. Frustration both in terms of layout and an in terms of execution of the final shape.

Fact is, I have found that one of the best ways to complete this problem is to use a run of the mill router equipped with a Micro Fence Circle Jig using the Ellipse option. Micro Fence produces awsome tools and their contruction and execution are OLIVER-IZED!

Nobody cuts a circle or ellipse or oval as well as the Micro Fence system in terms of setup, ease of use, accuracy and first time use success. Its worth checking these guys out. They often keep a lower profile than they should.

[Larry Crim]

Thanks all that site was exactly what I was looking for it explains tods version so even I can understand it, Would go with a micro fence that was my first thought but with xmas its just not in the budget right now maybe down the road.
Thanks again
Larry

[Alex Berkovsky]

I just had to draw an ellipse for the demilune table I am making - I used the same method that I linked to above. In the future, I'll be making this simple jig (http://www.popularwoodworking.com/features/fea.asp?id=1260).

[Frank Chaffee]

Thanks tod.

Excellent description.

Frank

[Doug Shepard]

...Fact is, I have found that one of the best ways to complete this problem is to use a run of the mill router equipped with a Micro Fence Circle Jig using the Ellipse option. Micro Fence produces awsome tools and their contruction and execution are OLIVER-IZED!

Nobody cuts a circle or ellipse or oval as well as the Micro Fence system in terms of setup, ease of use, accuracy and first time use success. Its worth checking these guys out. They often keep a lower profile than they should.

I don't have their ellipse option, but I've got to second that re: their circle jig. Makes things positively easy and it's super accurate.

[Jim Kountz]

Alex, that jig is the berries man. I built one of these things years ago and attached a plunge router to it also. Works like a charm everytime! Its so easy to build and use I cant imagine why anyone would want anything else. Give it a try folks, you wont regret it!

[Dale Thompson]

The problem with an oval is that its a circle with two centers or an ellipse in which you have two back to back parabolas with dual opposing foci.


Dev,
Are you SURE about the above sentence. :confused: Not that it matters, but we must be remembering different equations from our younger years. :) :D As a child, I remember Galileo clearly explaining to me that the Earth is NOT the center of the Universe. :mad: I turned him in for treason! :cool: :) :D

Dale T.

[Dev Emch]

That is what I told that spanish dude with the three boats... but we think he fell off the edge of the world.

[tod evans]

no lacquer this morning so my one functional cell remembered that it`s quite easy to discribe one quadrant of an ellipse with a stick and a framing (or larger) square.. drill a hole in a stick for a pencil, from the tip of the pencil measure the semiminor axis on one side and place a nail protruding as much as the pencil. do the same for the semimajor axis, then registering the nails on the arms of the square draw one quadrant with the pencil....flip the square and continue..this method is far more accurate than the string method...tod

[Dale Thompson]

That is what I told that spanish dude with the three boats... but we think he fell off the edge of the world.

Dev,
He can't say that I didn't WARN him. :cool: What of waste of three boats and their crews - right into the jaws of the sea monster - unless he went off the edge first! :eek: :D :)

Dale T.

[Dev Emch]

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.:D

[Dale Thompson]

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? :confused: :)

Tell me where I am wrong. :)

Dale T.

[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

[David Pettibone]

:rolleyes: Simple:rolleyes: 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.:D

David "just having fun" Pettibone

[Dale Thompson]

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.

[tod evans]

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

[Dale Thompson]

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. :D 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. :eek: 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! :cool: :)

Dale T.

[Jeff Horton]

In the future, I'll be making this simple jig (http://www.popularwoodworking.com/features/fea.asp?id=1260).

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.

[tod evans]

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

[Jeff Horton]

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

[Dale Thompson]

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! :D ). 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! :eek:

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? :confused:

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

Dale T.

[scott kinninger]

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_decorative_furnishings/article/0,2049,DIY_14441_2277964,00.html