Press Fit Calculator
Enter shaft, bore and hub diameters, materials, length and friction to get the Lamé contact pressure, press-in force, holding torque and axial load, hub stress with a yield check, and the temperature to heat the hub (or cool the shaft) for a shrink fit. Pick an ISO 286 fit such as H7/s6 to get its interference limits.
Interference fit contact pressure from the Lamé thick-wall equations is p = δ ÷ [d·(C_hub/E_hub + C_shaft/E_shaft)], with C_hub = (D² + d²)/(D² − d²) + ν_hub and, for a solid shaft, C_shaft = 1 − ν_shaft.
Use the Press Fit Calculator
ISO 286 fit picker (hole basis H7)
Hole and shaft limits and the interference range per ISO 286-2, for nominal sizes over 3 mm up to 400 mm (s6 up to 180 mm).
Size the torque on the minimum interference and check hub stress at the maximum.
Unit System
Geometry
Materials
Friction Coefficient
Typical: dry steel 0.12–0.15, lubricated 0.08–0.10.
Shrink-Fit Assembly
Shrink-Fit Temperature
Calculation Breakdown
Fill in the parameters and click Calculate.
ISO 286 interference table — H7 hole with k6 to s6 shafts
Minimum to maximum diametral interference in micrometres (µm) for common nominal sizes, from the ISO 286-2 limits (hole H7 = 0 to +IT7, shaft ei to ei + IT6). A negative minimum means the fit can have clearance (transition fit).
| Size (mm) | H7 hole | H7/k6 | H7/n6 | H7/p6 | H7/r6 | H7/s6 |
|---|---|---|---|---|---|---|
| 6 | 0 / +12 | −11 to 9 | −4 to 16 | 0 to 20 | 3 to 23 | 7 to 27 |
| 10 | 0 / +15 | −14 to 10 | −5 to 19 | 0 to 24 | 4 to 28 | 8 to 32 |
| 16 | 0 / +18 | −17 to 12 | −6 to 23 | 0 to 29 | 5 to 34 | 10 to 39 |
| 20 | 0 / +21 | −19 to 15 | −6 to 28 | 1 to 35 | 7 to 41 | 14 to 48 |
| 25 | 0 / +21 | −19 to 15 | −6 to 28 | 1 to 35 | 7 to 41 | 14 to 48 |
| 30 | 0 / +21 | −19 to 15 | −6 to 28 | 1 to 35 | 7 to 41 | 14 to 48 |
| 40 | 0 / +25 | −23 to 18 | −8 to 33 | 1 to 42 | 9 to 50 | 18 to 59 |
| 50 | 0 / +25 | −23 to 18 | −8 to 33 | 1 to 42 | 9 to 50 | 18 to 59 |
| 60 | 0 / +30 | −28 to 21 | −10 to 39 | 2 to 51 | 11 to 60 | 23 to 72 |
| 80 | 0 / +30 | −28 to 21 | −10 to 39 | 2 to 51 | 13 to 62 | 29 to 78 |
| 100 | 0 / +35 | −32 to 25 | −12 to 45 | 2 to 59 | 16 to 73 | 36 to 93 |
| 120 | 0 / +35 | −32 to 25 | −12 to 45 | 2 to 59 | 19 to 76 | 44 to 101 |
| 160 | 0 / +40 | −37 to 28 | −13 to 52 | 3 to 68 | 25 to 90 | 60 to 125 |
| 180 | 0 / +40 | −37 to 28 | −13 to 52 | 3 to 68 | 28 to 93 | 68 to 133 |
| 200 | 0 / +46 | −42 to 33 | −15 to 60 | 4 to 79 | 31 to 106 | — |
| 250 | 0 / +46 | −42 to 33 | −15 to 60 | 4 to 79 | 38 to 113 | — |
| 300 | 0 / +52 | −48 to 36 | −18 to 66 | 4 to 88 | 46 to 130 | — |
| 400 | 0 / +57 | −53 to 40 | −20 to 73 | 5 to 98 | 57 to 150 | — |
Sizes on a range boundary use the lower range (ISO 286 ranges are "over a, up to and including b"). s6 is listed to 180 mm. Sources: ISO 286-2 limit tables as published by CADforum and Emile Maurin (IT grades, k6, n6, p6, r6) and the SDP-SI Metric Handbook D815 tolerance chart (s6). Check the drawing's edition of ISO 286 or ANSI B4.2 before production.
Quick answer
Interference fit contact pressure from the Lamé thick-wall equations is p = δ ÷ [d·(C_hub/E_hub + C_shaft/E_shaft)], with C_hub = (D² + d²)/(D² − d²) + ν_hub and, for a solid shaft, C_shaft = 1 − ν_shaft. For a 50 mm steel shaft in a 100 mm steel hub with 0.05 mm diametral interference, p = 78.75 MPa. Press-in force is F = μ·p·π·d·L (74.2 kN at μ = 0.10 and L = 60 mm) and holding torque is T = μ·p·π·d²·L/2 (2,227 N·m at μ = 0.12). A 50 mm H7/s6 fit gives 18 to 59 µm of interference.
Examples
| Ø50 mm fit (hole H7: 0 / +25 µm) | Shaft limits | Interference | Typical use |
|---|---|---|---|
| H7/k6 | +2 / +18 µm | −23 to +18 µm (transition) | Locating, easy assembly |
| H7/n6 | +17 / +33 µm | −8 to +33 µm (transition) | Tight locating, light press |
| H7/p6 | +26 / +42 µm | 1 to 42 µm | Light press, can be dismantled |
| H7/r6 | +34 / +50 µm | 9 to 50 µm | Press fit for steel hubs |
| H7/s6 | +43 / +59 µm | 18 to 59 µm | Medium drive fit, permanent |
Pick an ISO fit and press "Calculate at max interference", or enter your own diameters, materials and friction.
Summary
The calculator treats the hub and shaft as thick-walled cylinders (Lamé equations, as in Shigley) to turn diametral interference into contact pressure, then gives the force to press the parts together, the torque and axial load the joint holds before slipping, and the hoop and von Mises stress at the hub bore with a safety factor against yield. An ISO 286 picker gives the hole and shaft limits and the minimum, mean and maximum interference for H7/k6, n6, p6 and r6 fits from 3 to 400 mm and H7/s6 up to 180 mm, and a shrink-fit section returns the hub heating (or shaft cooling) temperature for assembly. Units switch between mm/MPa and in/psi.
How it works
- Pick a nominal diameter and an ISO fit (for example H7/s6) to see the hole and shaft limits and the interference range, then press a button to load the minimum, mean or maximum case.
- Or enter the shaft diameter, bore diameter, hub outer diameter, shaft bore (0 for solid) and contact length yourself.
- Choose the hub and shaft materials (E, ν and expansion coefficient fill in) and the friction coefficients for pressing and for holding.
- The tool computes contact pressure p = δ ÷ [d·(C_hub/E_hub + C_shaft/E_shaft)], press force F = μ·p·π·d·L, holding axial force and torque T = F·d/2.
- It reports hub hoop stress and von Mises stress at the bore against the hub yield strength, and the temperature rise ΔT = (δ + clearance) ÷ (α·d) for shrink-fit assembly.
Use cases
- Checking that a gear, pulley or coupling hub transmits the required torque without keys.
- Sizing the press (tonnage) needed to assemble a bushing, pin or bearing seat.
- Choosing between H7/p6, H7/r6 and H7/s6 for a shaft size and checking the minimum interference still holds the load.
- Checking that the maximum interference does not yield an aluminium or cast-iron hub.
- Setting the oven or induction-heater temperature for a shrink fit, or the cooling needed with dry ice or liquid nitrogen.