Originally Posted by
unterhausen
I know the people that have done fatigue tests on unicrown fork found that they failed at the weld. And it's true that most "death forks" have had a problem at the crown. OTOH, it's possibly not directly analogous to a rack mount, but there are plenty of pictures floating around on the internets of failed fork blades due to disc brake mounts. These are approximately where a low rider rack mount would go. Those are buckling failures though, not fatigue failures. At one time I was collecting bike failure pictures, but I gave up on it.
I don't know what use a hydraulic press would be to tell you if a hole in a blade would be safe, you need cyclic stress. The failure you would experience in practice is only loosely correlated to the buckling stress.
that's because a disk brake stresses a fork in ways a regular fork will never see. Short of a crash a regular fork sees a lot of vibration and the braking forces pushes on the blades from the brake pads to the drops, absorbing the stress. On the other hand disk brakes attempt to twist the tip of the blades off.
As I mentioned were I to kill some forks I would do both, a hydraulic press and a shock test. It may be pointless but half of hobbies are like that.