Corner bend radius
Inside sheet bend radius should be equal to or greater than the sheet thickness. Sheet metal flow may get affected due to sharp inside edges causing fractures in some materials. It is advised to keep uniform radiuses across the design for the ease of tool making.
Minimum flange length of thrice the sheet thickness plus the corner bend radius should be maintained to prevent fracture at the corner bends.
Ideally, the hole diameter should be more than or equal to the sheet thickness. And should be twice the sheet thickness for hard metals. Small dimension punches are prone to failure during punching operations.
Gap between the holes
The below diagram highlights the minimum required distance between the holes to prevent issues during forming operations.
Cutout distance from the corner bend
The below diagram highlights the minimum distance required from the corner bend. Should be thrice the sheet thickness plus the inside bend radius.
Corner bend relief
To prevent any fracture at the corner during forming operations, bend relief is provided. Relief height should be greater than twice the sheet thickness plus the corner radius.