Enjoy 10% off your first order with code FIRST10 — max $500 discount. Start an Instant Quotehello@rivcut.com
Get an Instant Quote
Currently accepting new projects
Calculator

Press Fit Calculator

Find the interference, pressure, force, and stress for your press fit. Enter hub and shaft sizes, pick your materials, and see results update in real time.

Quick Answer: What Is a Press Fit?

A press fit (also called an interference fit) is a fastening method where a shaft is machined slightly larger than its mating hole, creating a permanent joint through elastic deformation when the parts are forced together. The interference generates contact pressure at the interface, which provides the holding force. Press fits are governed by ISO 286 tolerance classes and are commonly used for bearing installations, gear-to-shaft assemblies, dowel pins, and bushings.

This calculator uses Lamé's thick-wall cylinder equations to compute: diametral interference (mm or inches), interface pressure (MPa or psi), required assembly force (N or lbf), and von Mises equivalent stress in the hub to verify it stays below yield strength. Inputs include shaft and hub dimensions, material properties (Young's modulus, Poisson's ratio, yield strength), and ISO 286 fit class.

Typical press fit interference values: Light press (H7/p6): 0.001–0.025 mm | Medium press (H7/r6): 0.015–0.040 mm | Heavy press (H7/s6): 0.025–0.060 mm for a 25 mm nominal diameter.

Fit Details

Interference: 0.0010 in

Results

Interface Pressure
0 psi
Diametral Interference 0.0000 in
Assembly Force 0 lbs
Hub Hoop Stress 0 psi
Safety Factor --
Lame's Equation:
P = δ / (d × (C_hub / E_hub + C_shaft / E_shaft))
where C = (r²_out + r²_in) / (r²_out − r²_in)
Force = μ × P × π × d × L
Get This Press Fit Quoted

Uses Lame's thick-wall cylinder equations. Verify critical designs with FEA.

How Press Fits Work

A press fit holds two parts together with friction. The shaft is slightly bigger than the hole. When you push them together, the hub stretches and the shaft compresses. This creates contact pressure that locks the parts in place.

Interference

Interference is the size difference between the shaft and the hole. More interference means more grip. Too much interference can crack the hub. This calculator shows you the safe range.

Interface Pressure

Lame's equation finds the contact pressure between the shaft and hub. It uses the wall thickness, diameters, and material stiffness of both parts. Stiffer materials create higher pressure for the same interference.

Assembly Force

The force needed to push the shaft into the hub depends on three things: interface pressure, contact area, and friction. A longer press length or higher friction needs more force. Lubrication lowers the friction and makes assembly easier.

Pro tip: Heat the hub or cool the shaft before assembly. A 200°F temperature change on aluminum adds about 0.002 inches of clearance per inch of diameter.

Hoop Stress and Safety Factor

Hoop stress is the tension in the hub wall. It is highest at the bore surface. The safety factor compares this stress to the material yield strength. Keep the safety factor above 2.0 for most applications.

Frequently Asked Questions

A press fit joins two parts by pushing a shaft into a slightly smaller hole. The tight fit creates friction that holds the parts together without glue, bolts, or welds.
Most press fits use 0.001 to 0.003 inches of interference per inch of shaft diameter. Light fits use less. Heavy-duty fits use more. This calculator shows you the exact stress so you can pick the right amount.
Lame's equation calculates the pressure and stress in thick-walled cylinders. It tells you how much force the hub wall can handle before it yields. This calculator uses it to find the interface pressure between your shaft and hub.
Yes. This calculator supports different hub and shaft materials. A steel shaft in an aluminum hub is common. The material stiffness (elastic modulus) of each part affects the interface pressure and required force.
Steel shafts pressed into aluminum hubs are the most common combination. The difference in elastic modulus creates good interface pressure without excessive stress. Steel-to-steel, stainless-to-aluminum, and bronze-to-steel are also common. Avoid pressing two materials with similar thermal expansion coefficients if the assembly will see temperature changes.
Assembly force equals the friction coefficient times interface pressure times the contact area (pi times diameter times press length). Typical friction coefficients range from 0.1 for lubricated fits to 0.3 for dry steel-on-steel. This calculator computes the exact force based on your dimensions and materials.
A press fit uses mechanical force to push the shaft into the hub at room temperature. A shrink fit heats the hub to expand the bore, slides the shaft in, then lets it cool and contract. Shrink fits are used for larger interferences where press force would be impractical, or when you need to avoid surface damage.
A safety factor of 2.0 or higher is recommended for most press fits. Critical applications like aerospace or automotive should use 3.0 or higher. If the safety factor shown is below 1.5, consider reducing the interference, using a hub with a larger OD, or switching to a stronger hub material.
Press fits can sometimes be disassembled with a hydraulic press, but the interference will be reduced due to surface deformation. For assemblies that need to be serviced, consider a light press fit (H7/p6) or a shrink fit. Heavy press fits (H7/s6, H7/r6) often damage the bore surface and are not practically reusable.

Common Press Fit Classes (ISO 286)

Fit Class Type Typical Interference Application
H7/p6Light Press0.001" - 0.002"Bearings, bushings, removable assemblies
H7/r6Medium Press0.001" - 0.003"Gears, pulleys, permanent assemblies
H7/s6Heavy Press0.002" - 0.004"Shafts, high-torque couplings
H7/n6Transition+0.001" to -0.001"Locating pins, alignment features
H7/k6Transition0 to -0.001"Keyed assemblies, light duty
Our Capabilities

Press Fit Machining at RivCut

We machine interference fit components daily for aerospace, robotics, automotive, and industrial clients. From prototype press fits to production runs.

Tight Tolerances

We hold ±0.0002″ on bore diameters and shaft ODs. Our machines maintain consistent interference fit dimensions across production runs of any size.

Press Fit Materials

Steel, aluminum, brass, titanium, stainless steel, and Delrin. We regularly machine dissimilar material pairings — steel shafts into aluminum hubs is our most common press fit job.

Quality & Inspection

Every press fit component gets CMM inspection. We verify bore roundness, surface finish (Ra 16–32 for optimal friction), and dimensional accuracy. Full documentation available.

Get a Press Fit Quote
Free Engineering Review

Get Free DFM Feedback on Your Press Fit

Upload your CAD file or drawing and our engineers will review your interference fit design for free. We check tolerances, material compatibility, surface finish, and assembly feasibility.

  • Tolerance stack-up review for your hub & shaft assembly
  • Material pairing recommendations for your application
  • Surface finish optimization for target friction coefficient
  • Assembly method guidance (press, thermal, cryo-fit)
Upload CAD for Free DFM Review Learn About DFM

Accepts STEP, IGES, SolidWorks, Fusion 360 · Response within 24 hours · No obligation

Related Resources

Explore

More Resources

Part Drawing Template & Guide | What to Include Drill Bit Size Chart | Number, Letter & Fractional Sizes Free FAI Checklist Generator | First Article Inspection Free Invoice Generator | Create & Download Invoices Threading Standards Guide | UNC, UNF, Metric & NPT Sheet Metal Thickness Gauge Chart | Gauge to Inches & mm Tolerance Fit Chart | Clearance, Transition & Press Fit Reference CNC Design Guide | Rules for Machinable Parts
Ready to Start?

Get Exact Pricing for Your Parts

Upload your CAD file and get instant AI pricing. Prototypes ship in as few as 3 days. No minimums required.

Get an Instant Quote Email Us

No minimums · 100% Made in USA · Never brokered · Ships anywhere in the US

Ready to machine your part?

Upload CAD for Instant Quote