Here’s what the part started out looking like:
How I designed this part was that I needed the part to end up being 2 1/8 inches wide. With it being made out of 1/8 inch plate, this would result in a 1 7/8 inside dimension. Using a formula I found on the web
Bend Allowance = Angle * (Pi / 180) * (Radius + K-Factor * Thickness)
I needed to bend the material 90 degrees and using a 1/4″ radius of 1/8″ thick material. Using these values the formula looks like:
0.278 = 90 * (3.14 / 180) * (.125 + .42 * .125)
Where 3.14 is the value of Pi, 0.125 is the decimal value of 1/8″. I’m using the inside radius of 1/8″ and material thickness of 1/8″ and using the K-Factor of .42. K-Factor is the portion of the material where there will be stretching or shrinking.
Solving for this results in a distance of 0.278 inches. This is close to 9/32 inches or a little bit more than 1/4 of an inch.
How I refected this in my drawing was that I drew the inside shape, then added the bend allowance and then drew the side shape. Because I don’t have a press brake and this piece is about 5 inches long, I made a 1/8 wide cutout and left two tabs about 1/4″ wide.
This allows me to bend the part by hand and then weld up the edge. Here’s how it looks as I start to bend up the part.
Flipping it over I can bend up the other side.
All that’s remaining is the top part. Here I didn’t make a relief cut, I should have, and I did put in a relief cut for the side radius, but I put it a bit too high so it didn’t really help me make this bend. After a lot of hammering here’s what the part looks like.
Here’s how the part compares to the original:
After I was done with welding up the part and grinding the welds, I wanted to see how close I was to my original specs. I got the radius spot on at 1/4 inch, but I’m about 1/8 inch too wide. It doesn’t matter for this part, but I’ve figured out where I’ve gone wrong with my measurements and I’ll correct it in my TurboCAD drawing.