Ellipses Made Easy.

knucklehead

Here is the way I do an arch for a cased opening


Lay out the width of your opening your material


Mark the center


Mark your drop and draw a line from that point to the top center





Find the center of that and square down to the center of your opening,


This determines your radius and pivot for scribing your arch




Presto

Leo G

That is a radius not an ellipse. Radiuses are simple. But each has its place.

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Tom Struble

what kind of hammer is that?

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Leo G

Stiletto Tools Ti-Bone Titanium Hammer ?

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Gus Dering

In case anyone is wondering what an ellipse is;

If you have a triangle, any triangle, keep the base the same size and connect all the dots of the apex created by all the triangles created with the same circumference.

Take this ellipse as an example.



The triangle shown has a base of 51 15/16" and two sides of 30" each. Visualize keeping the sum total of those two lines the same as it moves right or left from this point and the trail left behind is the elliptical shape.

That is why the two nails and a string trick works.

The hidden concept of how to lay out an ellipse to fit any opening is also displayed in that diagram. The key is to locate those two "significant points".

Those points are easily found by scribing an arc from the apex across the long axis with a radius of 1/2 the length of the long axis.

If you were to tack 3 nails at the corners of that triangle, then snug up some non stretch fishing line around them and lock it in place with a split shot weight. Then pull the top nail and stretch it tight with your pencil. Scribe the arc.

This is best done with your larger elliptical openings that are two large for the other jigs described earlier.

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wallmaxx

http://www.finehomebuilding.com//ite...an-ellipse-ish

Watch the video

D.Foster

I've done this before and it actually only produces a radius, not an elipse. I think thats why they put the "ish" at the end. I posted it under carpentry. Its a good technique though for sure

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