"Cope cut" layout in large diameter pipe

[Woodscaper]

Anybody have short cuts on layout and cutting a 90 degree cope/saddle cut in a 20" diameter .250 wall pipe?
I have the cutting tools, just need layout advice.
Thanks.

[JGZ]

Cut out a 20" circle on poster board ,lay that down and trace it.

[Dirtheadz]

I thought their used to be a formula for large pipe, something like 1/4 of the diameter. Hell... I really did drop out & become a statistic, when I thought I wanted to be a mechanical engineer.

[Woodscaper]

Here is a formua:
X = (R1/Sin (JA)) - (((R1 - Sqr(R1^2-(Cos ( AP ) * R2)^2)) / Sin(JA)) + ((Tan (90 - JA) * (Sin(AP) * R2))))
R1 = large radius
R2 = small radius
JA = Joint Angle
AP = AnglePosition

I also found a method of laying out a pattern.

[Unaweep]

You can purchase paper templates at your welding store, they aren't expensive and will last a lifetime and work on many sizes of tube/pipe and various degrees/angles.


Erik