Press-fitting gears and pulleys onto shafts is an axial assembly operation in which interference, alignment, force progression and support directly determine whether the structure remains dimensionally stable and functional.
Gears and pulleys are sensitive to misalignment, point loading and local deformation of both hub and shaft. The pressing operation must proceed linearly, controlled and reproducibly. A hydraulic workshop press is suitable when the operation demonstrably falls within the technical boundary conditions of the press and the component geometry.
This page describes when mounting gears and pulleys falls within this application range – and when it does not.
When is a hydraulic workshop press suitable?
A hydraulic workshop press is suitable when:
- the mounting proceeds fully axially, without rotation or impact loading
- the pressing force is built up gradually and controllably
- the gear or pulley is guided straight onto the shaft without tilting
- the shaft is supported sufficiently over its length to prevent deflection
- force introduction takes place exclusively via the hub
- the interference fit is predictable and falls within a reproducible force band
When one or more of these conditions cannot be met, the operation falls outside the intended use of a workshop press.
Technical considerations
Pressing force & force build-up
The required pressing force is determined by:
- interference (Δd)
- shaft diameter
- hub length
- material combination
- surface roughness
- tolerance conditioning
Requirements for force build-up:
- the force must be built up step by step
- peak loading must not occur
- increase in resistance must be followed directly (indication for misalignment or contact issues)
- the hub must not be overloaded
Minimal misalignment causes an asymmetrical pressure profile that deforms the hub and locally locks the fit. This sometimes leads to a sudden force peak that loads the shaft laterally.
Interference, alignment & support
A stable mounting requires:
- exact axial alignment before building up force
- force introduction exclusively via the hub, never via teeth or belt-running surfaces
- full, stiff support of the shaft to prevent buckling or bending
- use of guide sleeves or receiving bushings that follow the hub profile exactly
- absence of lateral force components
Even slight shaft bending affects the first millimetres of the stroke. This deviation determines the later gear mesh or belt path and can lead to permanent concentricity deviations.
Structural requirements for the press
A suitable workshop press has:
- a welded steel frame that minimises lateral deflection
- linear stroke guidance with constant geometry
- pressing tools that bear exactly over the hub diameter
- a flat and torsionally stiff working table for shaft support
- sufficient mass to dampen microvibrations and force peaks
Frame flex greater than 0.3–0.5 mm introduces a lateral force component. As a result, the hub deviates from the shaft, leading to misalignment in the driveline profile.
What is often underestimated in practice
- sensitivity of gears to minimal misalignment
- damage caused by force introduction on teeth, flanges or belt-running surfaces
- shaft bending due to insufficient support
- relevant variation in interference due to temperature, wear or tolerances
- force peaks due to overly rapid operation
- irregular force curve due to contamination or micro-deformation of seats
These factors determine whether the end result remains within concentricity and dimensional tolerances.
Typical operations within this application
- press-fitting gears onto drive shafts
- mounting pulleys onto motor and transmission shafts
- rework on mechanical transmissions
- maintenance operations in industrial drivelines
- series mounting in assembly and workshop environments
This list describes the operation type; not the suitability of a specific press model.
Relation to press classes (HD programme)
Classification within the HD programme is determined by:
- interference
- shaft diameter
- hub length
- interference conditions
- required force band
Light-duty press class (20–60 tonnes)
Suitable for:
- smaller gears and pulleys
- short hubs
- low to medium interference
- configurations in which shafts can be supported axially with ease
Medium-duty press class (80–160 tonnes)
Suitable for:
- typical gear and pulley dimensions
- shafts with stable geometry
- controlled and reproducible pressing forces
- standard workshop and rework operations
Heavy-duty press class (180–500 tonnes)
Suitable for:
- large gears and pulleys
- long hubs
- high interference
- situations in which maximum frame and guidance stiffness is necessary
The correct press class is determined by mounting conditions and force profile – not by pressing force alone.
When is a workshop press not suitable?
A workshop press is not suitable when:
- rotation or thermal mounting is necessary
- the shaft cannot be fully and stably supported
- the interference varies strongly or is unpredictable
- force introduction cannot take place exclusively via the hub
- misalignment cannot be structurally excluded
- structural damage to hub, shaft or teeth cannot be ruled out
Further navigation within the site
Based on this application, reference can be made to:
- the relevant press classes within the HD programme
- the available standard models
For operations that fall outside these boundary conditions, reference is made to the separate engineering and custom-built hydraulic press trajectory in which deviating component geometries and critical mounting conditions can be assessed.
Request technical evaluation
When mounting gears and pulleys falls within the described technical boundary conditions, a technical evaluation can be requested to position the application within the correct press class.