# Formula for making precise PIE CUT BENDS............!!!!

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**1**0.0 BAR

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Join Date: May 2005

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**Formula for making precise PIE CUT BENDS............!!!!**

To make precise pie cuts bends I have provided a nice simple formula.

This formula makes a bend that is whatever angle you desire.

CLR = Center Line Radius (radius of the bend measured through the center of the tubing)

D = Diameter of Tube _____

L = Length of long side of pie cut - the top of this pie cut -> \____/

Angle = angle to cut pie section which, this angle is measured perpendicular to the length of the tubing

Bend Angle = The angle of the bend

N = number of pie sections to complete bend

* means multiply

You want to make a bend that is 120 degrees, uses 3" diameter tubing with a CLR of 4", and 5 pie sections.

Angle = Bend Angle / ( 2 * N )

Angle = 120 / ( 2 * 5 )

Angle = 12

L = [ ( 2 * CLR ) + D ] * [ sin ( Angle ) ]

L = [ ( 2 * 4" ) + 3" ] * [ sin ( 12 ) ]

L = [ 8" + 3" ] * [ sin ( 12 ) ]

L = [ 11" ] * [ sin ( 12 ) ]

L = [ 11" ] * [ sin ( 12 ) ]

L = [ 11" ] * [ 0.208 ]

L = 2.288"

[size=16pt]L = 2.288"

Angle = 12 degrees

_____

Now you need to cut 5 of these -> \____/ with the top part measuring 2.288" in length.

This formula makes a bend that is whatever angle you desire.

CLR = Center Line Radius (radius of the bend measured through the center of the tubing)

D = Diameter of Tube _____

L = Length of long side of pie cut - the top of this pie cut -> \____/

Angle = angle to cut pie section which, this angle is measured perpendicular to the length of the tubing

Bend Angle = The angle of the bend

N = number of pie sections to complete bend

* means multiply

**L = [ ( 2 * CLR ) + D ] * [ sin ( Angle ) ]**

Angle = Bend Angle / ( 2 * N )Angle = Bend Angle / ( 2 * N )

**Example:**You want to make a bend that is 120 degrees, uses 3" diameter tubing with a CLR of 4", and 5 pie sections.

Angle = Bend Angle / ( 2 * N )

Angle = 120 / ( 2 * 5 )

Angle = 12

L = [ ( 2 * CLR ) + D ] * [ sin ( Angle ) ]

L = [ ( 2 * 4" ) + 3" ] * [ sin ( 12 ) ]

L = [ 8" + 3" ] * [ sin ( 12 ) ]

L = [ 11" ] * [ sin ( 12 ) ]

L = [ 11" ] * [ sin ( 12 ) ]

L = [ 11" ] * [ 0.208 ]

L = 2.288"

[size=16pt]L = 2.288"

Angle = 12 degrees

_____

Now you need to cut 5 of these -> \____/ with the top part measuring 2.288" in length.

**Here is an Excel ------sheet that t_cel_t created that uses this formula for you mathematically challenged individuals. Pie Cut Excel Sheet****EDIT***

Here's the downpipe and mani I did for my car. It's 3", uses 5 pieces per 90*, and has a CLR of 3"[/size]Here's the downpipe and mani I did for my car. It's 3", uses 5 pieces per 90*, and has a CLR of 3"

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**5****Re: Formula for making precise PIE CUT BENDS............!!!!**

Originally Posted by

**CSaddict**My formula is eyeball x pipe / radius of the imaginary pipe in my mind= close enough.