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Thread: Calculating Pull Force Based on Bolt Torque

  1. #1
    Associate Engineer
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    Apr 2016
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    Calculating Pull Force Based on Bolt Torque

    Hi all,

    Let me start by saying I have looked at the bolt clamp force torque calculator found here:
    http://www.engineersedge.com/calcula...orque_calc.htm
    Maybe I am just not understanding the concept or incorrectly applying it to the project at hand.

    I am currently designing a pull tester to test and compare the strengths of various glues used here at work. I have to work with specific hardware and parts as the main concept was given to me to finish.


    As you can see in the attached picture, backing out the bolt on the right hand side will pull the plate away from the rubber slug that is going to be used to test the adhesion qualities of the glue.

    What I am trying to determine is the force at which the glue fails based on the torque applied to the bolt. It is quite possible I am overlooking something, hopefully someone can point me in the right direction.

    Thanks,


    Matt
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  2. #2
    Administrator Kelly Bramble's Avatar
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    Feb 2011
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    Bold Springs, GA
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    2,207
    The axial force vs torque calculator relies on a generic equation that utilizes friction as a variable. I doubt you'll get consistant readings or accuracy. Moreover, as the threads wear the friction will change creating more variability.

    I recommend you look at load cells for a more accurate and consistent readings..
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

  3. #3
    Technical Fellow jboggs's Avatar
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    Mar 2011
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    Myrtle Beach, SC
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    I agree with Kelly. Too many other sources of friction here to rely on the device's accuracy, and not just the screw. Those guide rods will not remain parallel as the screw is turned unless you add some good low friction linear bearings. Then you have the friction caused by very minor misalignments and inaccuracies in the parallelism of the rods and the bearings. A load cell mounted close to the glue application joint takes all those factors out of consideration.

  4. #4
    Associate Engineer
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    Apr 2016
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    Thank you kelly and boggs, I will look into using load cells. It may even be something we could make here as we develop transducers.

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