Published on: 03 November 2025
Acute angle in your part? Your attention is required!
It is relatively easy for customers to order bent parts with obtuse angles (> 90°) and angles of exactly 90°. But what if you need an acute angle (< 90°)? Then you need to pay slightly more attention, and not just to using the correct radius, but also to how your design may be adapted.
To explain exactly why, we will cover the following questions:
- How does Sophia® handle the radius of bent parts?
- Why are obtuse and right angles easier?
- Why do I need to pay more attention to acute angles?
- How should I deal with acute angles?
1. How does Sophia® handle the radius of bent parts?
Bent parts are always made from a flat sheet, which is known as the flat pattern. This flat sheet is slightly ‘shorter’ than your bent part, because the metal on the outside of the bend radius stretches slightly (and becomes longer) during the bending process.
When you upload a 3D part to be bent, our Sophia® online software must generate a flat pattern. The calculation process depends on many factors, including the angle in the drawing, the chosen material, the sheet thickness, optional settings and the available tools.
At 247TailorSteel, we source the required radius from a database with dozens of values accumulated through years of practical experience and careful testing on our bending machines. By using this radius, we can be sure that we can realise your dimensions within our tolerances.
Our Sophia® online software can extract the radius from your drawing and replace it with the correct radius from our database. This impressive technological innovation and our manufacturability check allow us to process large and automated sheet metal bending jobs and guarantee consistent quality.
However, it’s not quite that simple.
The technology works almost perfectly for bent parts with obtuse angles (greater than 90°) and angles of exactly 90°. However, there are other issues to take into account when it comes to acute angles.
2. Why are obtuse and right angles easier?
With obtuse angles and angles of exactly 90°, a slightly smaller or wider radius almost never affects the leg lengths of your product. The image below shows why.
The image above shows that if we use a wider radius, the lengths of the legs will remain the same. In most cases, the exact radius doesn’t matter, but the leg lengths do.
Please note: The difference between the radii above has been exaggerated to make clear that the flange lengths remain the same. In practice, our radius will be much closer to the radius in your drawing.
3. Why do I need to pay attention to acute angles?
With acute angles, a slightly smaller or wider radius does affect the leg lengths. Take a look at the example below:
The above image shows that the leg lengths become much shorter if the radius increases – and this is a relatively simple product.
If you have a part to be bent with (at least) one acute bend and many other bends, the entire part will be affected by this deviation. The dimension that remains after all the bends have been made is affected the most. We will illustrate this with an example as shown in the image below
.
The red part of the acute bend is included in the original drawing but will not be in the bent part, because the radius in the drawing will be replaced by a radius that can be realised in practice. This means the length of the red section will be deducted from the total length of the sheet to be bent.
On paper, the total length is 200 + 200 + 200 + 200 + 100 = 900 mm. However, in practice it will ‘only’ be 880 mm.
But which section will be shorter? It won’t be the section next to the acute angle, but one of the last lengths to be bent.
The image below shows what happens:
- Bend 1 is made so that flange 1 has a length of 200 mm.
- Bend 2 is made so that flange 2 has a length of 200 mm.
- Bend 3 is made so that flange 3 has a length of 100 mm.
- Bend 4 is made so that flange 4 has a length of 200 mm.
The result is that the dimension of flange 5 (the section that remains after all the bends have been made) will be 180 mm instead of 200 mm. This shows why the dimensional discrepancy doesn’t arise next to the acute bend, but elsewhere in your part.
4. How should I deal with acute angles?
If you don’t use our recommended radius when drawing an acute bend in your drawing, we must adjust the radius. This will affect the length, width or angle of the geometry of your part. However, we don’t know exactly which should be adjusted. Only you know that.
That’s why it’s important when drawing an acute bend to first determine the correct radius (which you can find here), and then to choose which solution is most appropriate for your situation:
- Adjusting the length
- Adjusting the width
- Adjusting the angle
We will explain each solution based on a practical example below to help you understand the possibilities.
See the image below.
This acute bend has been requested with a radius of 2 mm. However, we must use an inside radius of 1.14 mm to achieve the correct dimensions. Based on this information, you can choose to adjust the length, width or angle.
4.1 Adjusting the length
With this option, the bend moves closer to the vertex of the angle (as 1.14 mm is less than 2 mm). This means both legs of the bend will be longer.
Below you can see what will change and by how much.
This option is most appropriate when both the angle and the width of the lip are important, for example if it must fit over another part.
4.2 Adjusting the width
With this option, the bend radius remains in the same position and both legs retain the same length. This means the width of the bend will decrease.
Below you can see what will change and by how much.
This option is most appropriate when the width of the lip is not important but the length and the angle are, for example if side A must fit inside something.
4.3 Adjusting the angle
With this option, the bend radius remains in the same position, both legs retain the same length and the width remains the same. This means the angle of the bend will increase.
Below you can see what will change and by how much.
This option is most appropriate if the angle of the lip is not important but lengths A and C are. Examples include a drawer that must fit inside something else, with the acute angle used to create a handle.
The best option for your part depends entirely on your situation and what your product will be used for. We can’t make this decision for you, but hopefully this blog post will help you decide on the best option.
Questions about acute bends?
If you have further questions on this topic, please feel free to contact us.
