Modern Computer Aided Design or CAD in metal bending has automated traditional layout for the notch. But if you want to make better parts for your clients and impress them, you should know how these notched are made and measured.

If you could spend some time to learn how it works, you’ll be able to take better and efficient decisions regarding the notch in your metal part. You’ll know which notches are perfect for your job and select it from available ones in CAD menu. Trust me, it’s worth your effort.

The Lesson

First of all, you’ll need to know everything about the mold lines. On a flat pattern or on the drawing, the area of the radius that will be after forming is represented by the distance between two mold lines. Yes, there will be two of them, inside mold line and outside mold line.

But which line is outside and which line is inside?

This depends on which end of the metal part are you working on. Generally, the outside mold lines indicate the flange’s outer dimension and the inside mold line is actually a one bend deduction less. That is the subtraction value of the one bend deduction from the outer mold line location.

Once placed on a flat pattern, the mold lines work to reveal any small feature that lied on its radius. Therefore distort during forming while assuming that you achieved the expected radius in the metal part.

Two Axes, Two 90 Degree Bends

Sometimes, you’ll have two axes, thus two bends. They may be particular to one another. That means the metal part will have 2 side flanges with equal length, which are bent to 90 degrees.

To Layout desired notch, you need to use the mold lines again. Once we get to determine the inner and outer mold lines for each bend, we can define the center-line for them. We can do it by subtracting half a bend deduction.

The actual distance between the inner and outer mold lines is the one bend deduction. And the center-line splits up the distance, only a half a bend deduction for one mold line and another half a bend deduction for the second mold line.

Once we determine the centerlines, it is time for us to identify X-Y coordinates for both outer notch vertices. Now, the very point at which the center-lines intersect transforms to the innermost location. This is also called the top-center location of the notch.

However, if you are notching by your hand, it will be difficult to get the notch right.

But unless you are doing any prototyping work for a new stainless steel fabrication, aluminium fabrication, or steel fabrication project, you won’t even make the layout by hand. It’s just too much work and it’s not even worth it. So take some time to learn how notches work and then apply your knowledge to the corner selection in your CAD system. This will also help you in your laser cutting, metal rolling, welding or any other metal fabrication projects.