Quote Originally Posted by FloydHankers28 View Post
...... As to why all this is, I am assuming that the reason for this is because when someone brings in either a drawing or a file with the model, the sheet metal guys will normally figure out where and with what tools/dies to create the bends depending on your choice of material and what you're trying to accomplish. Hope this helps.
Words of wisdom, and I'd go even further and state that it is not "good engineering practice" to dimension bend lines or even the flat patterns themselves. The engineering drawing is a legal document that specifies your engineering intent, and as such should reflect the dimensions of the final part. IMHO the flat pattern has only two simple functions: 1. Confirmation that the part can in fact be manufactured using sheet metal, and 2. To present a suggested flat pattern that helps the manufacturer to estimate how much raw material to prepare, and the flat pattern should be marked as such on the drawing.
And last but not least, a dimension to a bend line is impossible to measure in the final part, so the manufacturer can't produce a COC (Certificate Of Compliance) and you yourself can't measure it either.