Press Fit Forces Stress Design Calculator

Torque Engineering and Design
Strength of Materials

This calculator will determine a variety of force, stress and other design parameters for press fit applications.

An interference fit, also known as a press fit or friction fit, is a fastening between two parts which is achieved by friction after the parts are pushed together, rather than by any other means of fastening.

For metal parts in particular, the friction that holds the parts together is often greatly increased by compression of one part against the other, which relies on the tensile and compressive strengths of the materials the parts are made from. Typical examples of interference fits are the press fitting of shafts into bearings or bearings into their housings and the attachment of watertight connectors to cables. An interference fit also results when pipe fittings are assembled and tightened.

Use this engineering calculator to determine engineering and design parameters for cylindrical press fit applications.

Related:

Press Fit Engineering and Design Equations (See Below)

  Enter numbers at BOLD Text Locations, Results in RED
  Loads Interference Parameters Equations Ref
  Torque to be transmitted (N-mm) torque Minimum required interface pressure (N/mm2) rPI  
  Axial force to be transmitted (N) force Differential Poisson radial interference due to axial force (mm) ddp 1
  Coefficient of friction mu Differential thermal radial expansion (mm) ted 2
  Operating temperature (oC)?? ot Outer body rotating inner diameter radial displacement (mm) robd 3
  Stress concentration factor at interface edge scf Inner body rotating outer diameter radial displacement (mm) ribd 4
  Rotation speed (rpm) rpm Total additional diametrical interference amount to be added (to ibod) (mm) addi  
  Outer body input parameters Interference Fit Calculations (Assumes addi has been added to ibod)  
  Outside diameter (mm) obod Maximum diametrical interference (mm) maxdelta ??(See diagrams)
  Interface diameter (mm) obid Maximum resulting interface pressure (N/mm2) maxip 5
  Plus tolerance (mm) obptol Minimum diametrical interference (mm) mindelta ??(See diagrams)
  Minus tolerance (mm) obmtol Minimum resulting interface pressure (N/mm2) minip 5
  Modulus of elasticity (N/mm2) obe Minimum safety margin (min obtained pressure/required pressure)    
  Yield strength (N/mm2) obsy Maximum sustainable torque (N-mm) maxt  
  Poisson's ratio obn Minimum sustainable Torque (N-mm) mint  
  Coefficient of thermal expansion (1/oC) obcte Minimum safety margin (min obtained torque/required torque)    
  Density (g/cm3) obrho Outer body material stresses at maximum interface pressure  
  Inner body input parameters Radial displacement of inner surface (mm)   6
  Engagement length (mm) L Radial press-fit stress at ID (N/mm2) obsr 7
  Intended outside diameter (mm) ibod Circumferential press-fit stress at ID (N/mm2) obsc 8
  Dimensioned outside diameter (mm)   Axial stress from applied axial Force (N/mm2) obsz 9
  Plus tolerance (mm) ibptol Shear stress from applied Torque (N/mm2) obtau 10
  Minus tolerance (mm) ibmtol Max radial centrifugal stress (N/mm2) obrc  
  Inside diameter (mm) ibid Max circumferential centrifugal stress (N/mm2) obcc 11
  Modulus of elasticity (N/mm2) ibe Max Von Mises stress (N/mm2) obvm 12
  Yield strength, obsy (N/mm2) ibsy Resulting safety factor (Yield stress)/(scf*Von Mises stress)    
  Poisson's ratio ibn Inner body material stresses at maximum interface pressure  
  Coefficient of thermal expansion (1/oC) ibcte Radial displacement of outer surface (mm)   13
  Density (g/cm3) ibrho Radial press-fit stress (N/mm2) ibsr 14
  Shrink-fit design Circumferential press-fit stress (N/mm2) ibsc 15
  Desired assembly clearance at deltaT (mm) ddt Axial stress from applied axial Force (N/mm2) ibsz 16
  Required differential temperature if heating outer body (oC) robdt Shear stress from applied Torque (N/mm2) ibtau 17
  Required differential temperature if cooling inner body (oC) ribdt Max radial centrifugal stress (N/mm2) ibrc  
  Press-fit design Max circumferential centrifugal stress at ID (N/mm2) ibcc 18
  Maximum assembly force to press fit (N) Fpfmax Von Mises stress at ID (N/mm2) ibvm 19
  Minimum assembly force to press fit (N) Fpfmin Resulting safety factor (Yield stress)/(scf*Von Mises stress)    
 
     
  Evaluate the stresses at inside, outside and sqrt(DiDo) diameters
  For the Outer Feature
  case 1: stresses at inner radius Case 2: stresses at outer radius Case 3: stresses sqrt(DiDo)/2
  Radial press-fit stress (N/mm2)
  Circumferential press-fit stress (N/mm2)
  Axial stress from applied axial Force (N/mm2)
  Shear stress from applied Torque (N/mm2)
  Radial centrifugal stress (N/mm2)
  Circumferential centrifugal stress at ID (N/mm2)
  Von Mises stress at ID (N/mm2)
  For the Inner Feature
  case 1: stresses at inner radius Case 2: stresses at outer radius Case 3: stresses sqrt(DiDo)/2
  Radial press-fit stress (N/mm2)
  Circumferential press-fit stress (N/mm2)
  Axial stress from applied axial Force (N/mm2)
  Shear stress from applied Torque (N/mm2)
  Radial centrifugal stress (N/mm2)
  Circumferential centrifugal stress at ID (N/mm2)
  Von Mises stress at ID (N/mm2)

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