elbows can be machined from a standard elbow
Other degrees elbows can be machined from a standard elbow. Longer radius type, the center to face dimension e.g. is three times the nominal size (, even is available.
Dimensions, dimensional tolerances etc. for long and short radius elbows are defined in ASME B16.9
The weakest point on an elbow is the inside radius. ASME B16.9 only standardizes the center to face dimensions and some "squareness" dimensional tolerances. The wall thickness at the weld line location even is standardized, but not through the rest of an elbow. The standard states that the minimum tolerance will be within 12.5% of the minimum ordered wall thickness of the pipe. A maximum tolerance is specified only at the ends of the fitting.
Many providers of buttweld elbows (and tees) provide one schedule greater thickness so that sufficient wall thickness, after forming, remains.
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