A Hex Bolt Half Thread is a form of threaded fastener with an external male thread. And bolts are very closely related to screws. These are grades 4.6 and 8.8. The first digit so relates to the ultimate strength of the material. Because the second is the ratio of yield stress to ultimate strength. Thus grade 4.6 bolts have an ultimate material strength of 400N/mm2. And the yield (or proof) stress is 60% of the ultimate strength. Grade 8.8 Bolts are manufactured using medium carbon steel that has been quenched and tempered. Used in railroad equipment, motors, engines, and processing equipment, grade 8.8 bolts exhibit good tensile strength and perform well in most environments. Grade 10.9 metric bolts are manufactured. Using medium carbon steel, medium carbon steel alloy, and low carbon boron steel that has been quenched and tempered. Used in automotive applications and for bolting large and forged parts, metric 10.9 bolts exhibit high tensile strength and good wear resistance. Hex Bolt Grade A – Intended for Hex Head Bolts and studs/threaded rod having a minimum tensile strength of 60 ksi in general applications. Grade B – Intended for Heavy Hex Head, these bolts, studs/threaded rods have a tensile strength of 60 to 100 ksi and are intended for flanged joints in piping systems with cast iron flanges.  Available Sizes From M6 to M56 Available Length From 25mm to 500mm Hot Forged Bolts and Nuts Dia From M30 to M72 Length  From 200 – 600mm