Looks like most of those grooves are with a radius nosed tool, some v-grooved. I was just questioned whether shape of concentration had much of an affect on shear angle and couldn't remember all the specifics from materials and mechanics of materials or if it really mattered in this instance as long as my cross section was what matched my preferred fail load. Also inducing some heat and entering the center of a larger sized bolt, which might have a different crystal structure at its interior.