Posted by admin on Wednesday, February 17, 2010 · Leave a Comment
I can't remember back to my days of learning about simple machines. I am working on a project that needs 100-250 psi of clamping force and want to figure out if my systems will be enough.
To get this force, I am tightening several nuts onto bolts with a wrench. I do not have a torque wrench and have no desire to buy one. I am just trying to do some theoretical math.
The wrench is 6 inches long. The bolt the nut is going onto is 3/8 diameter with 16 threads per inch (1/16 pitch).
Would calculating the mechanical advantage of the screw (bolt) and wrench and then adding them together and then multiplying that times the amount of force I could put on the wrench calculate the pressure per screw? If not how would you do it?
Mechanical advantage with screws is funky. You are better off using a bolt torque calculation. Mortals do not derive these, just look them up in a mechanical engineering design text or reference or on the net. Be aware that due to variation in friction coefficients and other problems, very modest accuracy. As a result, use of this method is generally discouraged...
Google things like "bolt tension torque calculation" for method and limitations.
For example, http://www.efunda.com/designstandards/screws/fasteners_intro.cfm
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