cracking frame bolts

[chooch75s]

I have not seen the details of the cracks on the bolts. Are they accross the shank? Or does the crack start at the bottom of a thread? This is significant because if the crack starts at bottom of a thread then the threads are probably cut instead of rolled. Cut threads produce 'stress risers' at the bottom of the cut and will quickly initiate a crack. Rolled threads force the metal grain pattern along the thread and will resist cracking. I hope that Kaw has a rolled thread called out on the screw specifications in this high fatigue application. If not, they should. Please be aware that getting a screw made with a stronger material may not solve the problem if the material has no fatigue resistance. Material strength often has no relationship with fatigue resistance. My suggestion: If you are buying 'stronger' screws, make sure that the threads are rolled.