[Amir]

If your bend radius in not critical then it is probably better to specify “Use Minimum Bend Radius.” Usually, with sheet metal, the goal is to get as close to 90 degrees as possible. If you specify the minimum, then the sheet metal fabricator will use the tooling set-up to achieve a bend that is as close to 90 degrees as possible without overstressing the material.

If you specify a specific bend radius then the sheet metal fabricator should technically try to hit that radius within your specified tolerances. If you have a close working relationship with your fabricator then they will either know what you are trying to do and just use the minimum or they will call you to confirm. If you just send it out to some faceless shop then they may use your specified radius and this could potentially cost more money.

Using the K factor can be helpful from an engineering design perspective so that you know which bend radius is possible, but putting this radius on your drawing is generally not necessary or advisable.

Hope this helps,

Amir