Stitch-welded elbows, while only available in Galvanized metal, are available up to a maximum of 22 gauge and a fixed radii of 1xD or 1.5xD.
These are elbows formed by stitch welding halves that have been stamped out using mechanical presses and forming dies. The stitch weld is virtually a continuous weld although a visual examination would lead one to think that the weld was an intermittent weld. HOWEVER, there is another weld on the reverse side welding the 'skipped space' from the other side. The result is a very tight elbow.
The mechanical stamping process places limits on the gauge that can be used, limiting them to a maximum of 22 gauge and a fixed radii of 1xD or 1.5xD. The result is that these elbows, while available in sizes 3",4",5",6",7", 8", 9", 10" and 12" in 90, 60, 45 and 30 degrees, are good all around elbows for air or dust up to 8". Larger than that their application should be limited to light dust or air as the gauge is too light for heavy particle.
The ends of the elbow can be fitted with flanges or rolled lips.