Q:  Hi, I need a 1.25” X 15” bolt that can operate in continuous temperatures of 1000F. Currently we are using a heat treated carbon based 4140 fabricated machined bolt. At these temps the bolts are “Stress Relaxing” and we are losing our clamping pressure. In addition, when we change the load to shear pressure, we are losing the bolts completely. Help!

A: For this situation, I think the most economical option for a high strength bolt that will maintain it’s strength at 1000F is A286 alloy. A286 stays strong to 1300F with an ultimate tensile strength of 167 ksi. A286 bolts will be oxidation resistant and will be a lot more creep resistant under loads.