1. Bent part with flanged hole (thread)
As shown in Figure 4-17. Its flanged (threaded) hole
The distance L from the hole wall to the bend edge cannot be too small, as this may damage the flange (even prevent its formation).
Generally, it is recommended to select L > (7~8)t based on experience. When the structural requirement of the bent part requires a shorter distance from the flanged (threaded) hole wall to the edge of the bend, the minimum distance must be calculated or determined graphically based on parameters such as material thickness t, flange hole (thread M ) (diameter D) size, flange height, bending shape and bending radius r.
Common Metric Thread Bottom Hole Flange Dimensions
See Table 4-5 for common metric threaded bottom hole flange dimensions. Examples of marking dimensions are shown in Figure 4-18.
Table 4-5 Bottom hole flange dimensions with common metric thread (unit: mm)
| Thread diameter d | Material thickness t | Flange inner diameter d 1 | Flange outer diameter D | Flange Height h | Pre-drilled hole diameter d 0 | radius of curvature r |
| M2 | 0. 6 | 1.6 | 2. 6 +0.16 | 1.3±0.2 | 0.8 ±0.1 | 0.2 |
| 0. 8 | 2.7 +0.16 | 1.6±0.2 | ||||
| 1 | 2. 9 +0.16 | 1.8±0.2 | 1.2 ±0.1 | 0.4 | ||
| M2.5 | 0. 6 | 2.1 | 2.9 +0.16 | 1.3±0.2 | 0.2 | |
| 0.8 | 3. 2 +0.16 | 1.7±0.2 | 1.0 ±0.1 | |||
| 1.0 | 3. 5 +0.16 | 1.9±0.2 | 0.4 | |||
| 1.2 | 3. 5 +0.16 | 2.0 ±0.2 | 1.2 ±0.1 | |||
| M3 | 0. 8 | 2.5 | 3. 6 +0.16 | 2.0 ±0.2 | 1.2 ±0.1 | 0.2 |
| 1.0 | 3. 6 +0.16 | 2.1 ±0.2 | 0.4 | |||
| 1.2 | 4. 0 +0.16 | 2.2±0.2 | ||||
| 1.5 | 4.2 +0.16 | 2.4±0.2 | 1.6 ±0.1 | |||
| M4 | 1.0 | 3.3 | 4.7 +0.16 | 2.6 ±0.2 | 1.6 ±0.1 | 0.4 |
| 1.2 | 5 +0.16 | 2.8 ±0.2 | ||||
| 1.5 | 5. 4 +0.16 | 3.0±0.2 | ||||
| 2.0 | 6 + 0.16 | 3.2 ±0.2 | 0.6 |
Note: This table is applicable for flange bottom thread holes of low carbon steel, brass, pure and aluminum. The data in the table is for reference only.
Example 4-1 illustrates a part bent as shown in Figure 4-17. The sheet thickness is t = 1.5 mm, the M4 thread is threaded into the flange, and the required flange height is H = 3.3 mm. Calculate the minimum wall distance from the flange hole (tapped thread) to the bent edge.
Solution: Use a 30° bending knife for processing and the graphical method to calculate the minimum distance from the wall of the flange hole (tapping thread) to the bending edge.
Using the graphic method, we obtain L=6mm.
2. Suggested minimum distance from flange hole wall (tapping) to bent edge
See Table 4-6 for commonly suggested minimum distances from the flange hole wall (tapped thread) to the bent edge.
Table 4-6 Suggested minimum distances from flange hole wall (tapped thread) to bent edge (unit: mm)
| Thread diameter d | Material thickness t | |||
| 1.0 | 1.2 | 1.5 | 2.0 | |
| M3 | 4.9 | 5.1 | – | – |
| M4 | – | 5.7 | 6.0 | – |
| M5 | – | 5.9 | 6.4 | – |
Note: The data in the table is for reference. Minimum values are generally not used.
