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Great idea. Haven't had a need to do that but good to know.

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i don't see anylinks to YouTube or diagrams on how to do this.

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The "Here" in @scottgrove 's original post is a link to:i don't see anylinks to YouTube or diagrams on how to do this.

As I said in my previous post I don't have the bandwidth, for curiosity's sake please tell me the short version.

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ThanksThe "Here" in @scottgrove 's original post is a link to:

As I said in my previous post I don't have the bandwidth, for curiosity's sake please tell me the short version.

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If the center point of the radius lies outside the walls of your shop or if there are obstructions in the way, you have to resort to something like what Scott Grove showed.

The other advantage is if you know width and height you want the arch, you don't have to know the radius. I have always used a formula to get the radius, but this don't need it.

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So he calculates it and plots it out X,Y?

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C = radius

L = length between end points on the arc

Run a line from the center point of the circle through a point that bisects L, That line will intersect the third point on the arc.

To simplify the math, use A as 1/2 L, C as the radius and B as the line from the center to the cord line.

A² + B

B² = C² - A²

B = The distance from the line to the arc is C - B

Example:

Radius = 20

Length between points = 6

From center point of circle to line is:

20² - 6² = 400 - 36 = 364

B =

= 19.078

Distance from center point of line to arc is 20 - 19.078 = .922 Ft = 11.064 inches

WOW!If you know the radius that you want and the distance between the outside points on the arc, here is how you calculate the middle point location.

C = radius

L = length between end points on the arc

Run a line from the center point of the circle through a point that bisects L, That line will intersect the third point on the arc.

To simplify the math, use A as 1/2 L, C as the radius and B as the line from the center to the cord line.

A² + B²= C ²

B² = C² - A²

B = The distance from the line to the arc is C - B

Example:

Radius = 20

Length between points = 6

From center point of circle to line is:

20² - 6² = 400 - 36 = 364

B =

View attachment 398114

= 19.078

Distance from center point of line to arc is 20 - 19.078 = .922 Ft = 11.064 inches

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