Another good source for information and fasteners is the McMaster-Carr catalog.
McMaster-Carr They show the strength, if available, for each cap screw or nut, for many materials and grades. A grade 8 3/8-16 cap screw is rated at 150,000 psi, a grade 5 at 120,000 psi, an inexpensive stainless (18-8) at 70,000 psi, and an expensive stainless (17-4PH) at 140,000 psi. The grade 5 costs 20 cents each and the 17-4PH costs $7.50 each. I have broken hardware store stainless steel cap screws by applying typical torque values.
Hoyt
