These custom tapered shoulder socket head bolts were manufactured using 4140 alloy steel material with 28-32 HRC hardness and zinc clear finish. The shoulder diameter tapers form 0.78" down to 0.75" and the head diameter was set to 1.00 +/-.015". Underneath the shoulder approximately .55" of 3/8-24 2A thread was rolled with thread relief allowance of roughly .085".
