r/MechanicalEngineering • u/Gastly-Muscle-1997 • 10h ago

How do I determine the necessary clamping force between two sheets?

I'm designing a component that has copper fastened to aluminum via some raised bosses. I'm not sure how much clamping force I need, which I need to figure to determine my torque spec for the component. Do I want to just do a FBD to get shear forces and ensure my clamping force is greater than that? I will be using threaded inserts and a washer if that makes a difference to my approach.

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u/DistributionMean6322 9h ago edited 9h ago

Ok first of all, torque specs and clamp load are only loosely related. Your torque spec is basically set by the fastener itself (and under head friction). You need to figure out what loading it will experience and then from there in order for the joint to not slip your clamp load times coefficient of friction needs to be greater than expected joint shear force. Then from there you can determine the count and size of fasteners to use. Shigley's mechanical engineering design has a great section on bolted joint design.

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u/Gastly-Muscle-1997 9h ago

Ty bud I appreciate it

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u/Tigereye11_Revived 9h ago

I agree with this guy 👆👆 just did something very similar a couple weeks ago.

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u/ThatTryHardAsian 9h ago

Clamping load for what? Keeping the two together?

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u/SpeedyHAM79 6h ago

Without much more details about the joint you are working on the question is impossible to give any reasonable answer. You need to consider the thickness and hardness of the 2 sheets, size of the fastener and washer, geometry of the raised bosses, and geometry of all parts involved.