Not that I am aware of any ASME standard specifically dedicated to sheet metal drawings, but what kind of information are you expecting to get from such document?
I do lots of sheet metal drawings. I am not aware of standards for them, separate from any other kind of fabrication drawing.
Sheet metal shops can bend to tolerances of ±.015" or ±0.4mm. Your tolerances to and from bends should reflect this.
I have never checked the accuracy of the punching or laser cutting or whatever. I assume they are pretty good.
I keep claiming here that any idiot can prepare drawings for machining. Sheet metal, casting and weldming is more difficult because the fabrication process will not automatically do the tolerances required to make your part work. You are going to have to think out your drawings and your design. Your design will have to work with the sloppier tolerances imposed by the process.
Go back and read the GD&T standard and any manuals you may have. This is where good GD&T becomes useful.
I know it is in German but if you look at the DIN/EN/ISO numbers listed you should be able to find it in English.
If not - you could have someone translate the important parts of the table.
A Y14 standard for sheet metal has been proposed several times, but there hasn't been enough interest/participation for it to move forward. If there is a base of people ready to work on such a standard, ASME would be the right forum to get it going. There has been significant cross-pollenation, historically, between DIN/ISO/ASME, with each basing some aspects of their standards on the others (or pretty much copying them entirely).
