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Home > Forums > Mechanical Engineers > Activities > Mechanical engineering general discussion > FAQs

Mechanical engineering general discussion FAQ

Internet Resources

Press Fits - quick calculator by GregLocock
faq404-1230
Posted: 8 Apr 06 (Edited 16 May 07)

The equations are called Lame's equations.

Here's an online calculator

http://www.tribology-abc.com

under interference fits. You have to log in to be able to change the pin diameter.

Alternatively desertfox looked up the equations, so you can roll your own:

Here are the formulas you need:-

 

          Pa= f*3.142*d*L*Pc

   where f=friction coefficient
         Pc=contact pressure between the two members
         d= nominal shaft dia
         L=length of external member.
         Pa= axial force required to interference fit

to calculate Pc for a given interference use the formula:-

Pc=x/[Dc*[((Dc^2+Di^2)/(Ei(Dc^2-Di^2))+((Do^2+Dc^2)/(Eo*(Do^2-Dc^2))-((Ui/Ei)+Ui/Eo))]

where x = total interference
      Dc=dia of shaft
      Di = inner dia of shaft(this is zero for solid shaft)
      Do= outside dia of collar
      Uo=poissons ratio for outer member
      Ui=poissons ratio for inner member
      Eo=modulus of elasticity for outer member
      Ei=modulus of elasticity for inner member

This formula for Pc will simplify if the materials are the same.

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