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Thread: Linear Force Generated by a SHCS

  1. #1
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    Linear Force Generated by a SHCS

    Hi all,

    I am trying to find a formula to calculate and check an existing spreadsheet I am working with.

    I have a 3/4-16 SHCS, I am putting 214.5 ft/lbs. in the screw and want to know what force the screw is exerting on a fixed object or how the force is multiplied through the fastener., or Linear Force Generated by said input.

    I am not interested in the Axial forces, Clamp Load or lifting capacity as that seems to be the only things that seem to come up on the web and here when I looked for it.

    Thanks in advance,

    Regards,
    Jim

  2. #2
    Technical Fellow Kelly_Bramble's Avatar
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    I'm not sure what you're looking for as I understand that...

    Axial forces, Clamp Load or lifting capacity = force the screw is exerting on a fixed object
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  3. #3
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    Hi again,I am deforming metal with a Jack screw, so I want to know if I input X force into a screw what is the forces exerted into the fixed object at the other end of the screw/metal being deformed.I have the following formula although not sure the variables:Formula:Torque to RaiseT = ((𝐹∗𝐷&#119898)/2 ∗((𝜋𝜇𝐷𝑚+&#119871/(𝜋𝐷𝑚 −𝜇&#119871)F = ((2∗&#119879)/𝐷𝑚 ∗((𝜋𝐷𝑚 −𝜇&#119871/(𝜋𝜇𝐷𝑚+&#119871)the variables I have are to enter from the spread sheet are the following:Screw Pitch Dia (in): [B1] 0.7094Threads per Inch: [B2] 16Screw Lead (Inch per thread): Formula =1/B2 [B3] 0.0625Coefficient of Friction: [B4] 0.65 (Steel on Steel)Torque Applied (In-Lb): FT-Lb: [B5] 214.5Linear Force Generated (Lb): formula=1/((1/B5)*((B3+(6.2832*B4*B1/2))/(6.2832*B1/2-(B4*B3)))*(B1/2/1)) [B6] 875.6216Not sure I am explaining it correctly, but attempting to validate the above spreadsheet is valid to calculate the force exerted by the screw.Thanks Again,Regards,Jim

  4. #4
    Agree with Kelly. "Axial force" means "force along the centerline axis", in other words it is the "linear" force I believe you are inquiring about. How is your force different from that?

  5. #5
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    Hi again,

    Sorry for the gibberish as not sure what happened as not how I had typed it.

    Think I found the inverse formula I need in the machinist handbook just need the inverse formula (any help would be appreciated) or solve for "Q" in the below formula which I guess might be the Axial Load

    Force-2024-04-16.jpg

    Regards,
    Jim

  6. #6
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    Hi Again,

    Think this is the formula I need can anyone confirm:

    Q = F X ((6.2832r + μp)/(6.2832μr p)) X (R/r)

    Regards,
    Jim
    Last edited by jim_moses; 04-17-2024 at 08:54 AM.

  7. #7
    Technical Fellow Kelly_Bramble's Avatar
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    Quote Originally Posted by jim_moses View Post
    Hi Again,

    Think this is the formula I need can anyone confirm:

    Q = F X ((6.2832r + μp)/(6.2832μr – p)) X (R/r)
    Your algebra is correct however do know that Q is still axial force applied by the screw and the variables are those related to 'the motion opposite of load Q"

    The unmanipulated equation for F is calculating the estimated force to initially unscrew the force Q applied by the screw.
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  8. #8
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    Hi again,

    Just to confirm if I put the said screw in a fixture and applied force to the lever (R) the output or Axial force is what I would see if the screw was sitting on a load cell correct?

    Regards,
    Jim

  9. #9
    Technical Fellow Kelly_Bramble's Avatar
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    Quote Originally Posted by jim_moses View Post
    Hi again,

    Just to confirm if I put the said screw in a fixture and applied force to the lever (R) the output or Axial force is what I would see if the screw was sitting on a load cell correct?

    Regards,
    Jim
    As with all analysis it is an nominal estimate with +/- variability.
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

  10. #10
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    Thanks,

    one more question as unsure what the units I should be using as I compared my spreadsheet to your calculator, Estimated Fastener Bolt Clamp Force Torque Calculator and I have put in Ft-lbs, but the wording seems to suggest inch-lbs

    either way I would have expected to be closer to Engineers edge calculator so what do I have wrong or am I figuring something different between the 2

    see attached:



    Regards,
    Jim
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