> I need to know the strength of a bolt. > > It is rated 10.9, so i think it's strength is 1000N/mm2 when pulling it. The first two numbers are ultimate tensile strength under which the bolt will fail. Multiply that by 100 to get N/mm2 or MPa, so your bolt has a UT of 10000 MPa. The number after the decimal is yield strength of the bolt. This is a percentage of the ultimate tensile, so in your case 0.9 of 10000 MPa or 90%. Yield stress is the amount under which you bolt will plastically deform...in other words it will not return to it's original shape after you have released the load. All fasterners should be designed around yield strength NOT ultimate tensile. > If i use this bolt to join 2 elements, which try to shift against each > other, how do i calculate the maximum force it can stand? Let's get some nomenclature out of the way... The type of joint that you pictured is called a single lap joint. The proper way to calculate the strength of that joint is extensive; one would have to cover a weeks worth of machine design to cover the topic. I recommend a library book on machine design or possible the Machinery's Handbook. Could you provide some background info on the joint in question? -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist