sheet metal so bends end up in the right place?

[graffian]

Never, pretty sure on that, have I bent sheet and not had to massage it cos I bent it in the wrong place. I had a scrap bit of L shaped(one bend) sheet, so a quick google and ai told me I had to subtract the setback. I wanted to turn my L shaped bit of sheet into a U shape that was 70mm across the outside of the flanges. With the ai help I ended up with a u shape 68mm wide. So how do I go about this sorta thing?

 

[Welderpaul]

Go by the internal measurements of the U shape and you should end up with the two bends in the right place.

What are the finished dims you need and what is the material thickness?

 

[droopsnoot]

I got a few spare pieces of different thicknesses, marked a line along them, folded them up based on the line against the folder blade, and keep those for a reference as to where the bend actually appears compared to where the line is drawn. It helps a bit, but I'm not as accurate as I'd like to be. It doesn't help that I can never be certain exactly how close to the blade I put it, or indeed which side of the line.

 

[RichardM]

I think the Zues book has bend radius calculations in it.