What are you making? Hand rail out of Angle Iron or Pipe?
Or
Are you trying to do Piping without fittings?
What size pipe?
What will be in the Pipe?
What is the planned flow rate?
What is the operating Pressure and Temperature?
Note there is no such thing as a "Single" piece Mitre Bend.
There are:
Two Piece/One Weld Mitre Bends
Three Piece/Two Weld Mitre Bends
Four Piece/Three Weld Mitre Bends
etc.
Mitre Bends can be made in any angle.
The main criteria for choosing which to use is based on the pressure drop of the fluid (or Gas) inside the pipe. For the same size pipe and the same flow rates the pressure drop is higher for the two piece/one weld mitre bend than for the four piece/three weld mitre bend.
The secondary criteria is the Stress concentration is higher in the two piece/one weld mitre bend than in one that has a higher number of pieces thus lower angle of incremental bend .
You may find a trimmed elbow is a better option if you are wanting a single segment option, which PennP is right there is no such thing as a single mitre.
Mitre Bends
Re: Mitre Bends
