Piston and Shoe Assemblies for Axial Piston Pumps
Piston and shoe assemblies for axial piston pumps, swaged and checked for shoe clearance with hydrostatically balanced bronze shoe faces.
Product Overview
The piston and shoe assembly slides in the cylinder block and rides on the swash plate through a thin film of oil. If the shoe clearance opens up, the film breaks down, the shoe face wears and metal goes round the circuit. We swage every shoe to the piston, then measure the clearance on each piece rather than on a sample, because a single loose shoe will take out a whole rotary group.
| Rexroth pattern frames | A2F A2FO A2FM A4V A4VSO A4VG A6V A6VM A7V A7VO A8VO A10VO A10VG A11VO A11VG |
|---|---|
| Supply | Sold as a full set for one pump or as individual pieces |
Key Benefits
- Shoe clearance measured on every piece, not sampled
- Bronze shoe face hydrostatically balanced so the oil film carries the load
- Supplied as a full set for one pump so all pistons match
- Piston outside diameter ground and gauged to the block bore
Application Scenarios
- Main pump rebuild on excavators and loaders
- Industrial power unit overhaul
- Motor rebuild on travel and winch drives
- Replacing one damaged assembly in an otherwise good set
Who It Is For
- Pump rebuild shops
- Maintenance workshops
- Distributors serving rebuilders
- Exchange unit builders
Problems It Solves
- A shoe has picked up and scored the swash plate
- Shoe clearance has opened and the pump has lost efficiency
- Contaminated oil has embedded particles in the shoe faces
- Only part of the set is damaged but mixed wear is a risk
Technical Features
- Case hardening steel piston, ground and gauged
- Bronze shoe face with hydrostatic balance pocket
- Swaged joint checked for retention and clearance
- Sets weight matched so the block runs in balance
- Available for the full range of frames we cover
Specifications
Performance figures depend on the exact variant, so we confirm them against your model code rather than publishing a number that may not apply to your pump.
| Piston material | Case hardening steel, carburised and hardened |
|---|---|
| Shoe face | Bronze, hydrostatically balanced |
| Joint | Swaged and clearance checked on every piece |
| Finish | Piston outside diameter ground |
| Supply | Full set for one pump or individual pieces |
| Packing | Oiled and vacuum sealed as a set |
Materials
| Cylinder blocks | Case hardening steel with a sintered bronze running face, bonded and machined after sintering |
|---|---|
| Pistons and shoes | Case hardening steel with a bronze shoe face, swaged and hydrostatically balanced |
| Valve plates | Bearing steel or bronze faced steel depending on the frame, lapped to a mirror finish |
| Drive shafts | Alloy steel, carburised and hardened on the spline and bearing seats, ground on centres |
| Vanes and rotors | High speed tool steel and case hardening steel, hardened and ground on all working faces |
| Cam rings | Bearing quality alloy steel, through hardened then profile ground |
| Seals | Nitrile as standard, fluorocarbon or polyurethane on request for hot or fire resistant fluid duty |
Manufacturing Process
- Turning and millingBlanks are turned and milled from certified bar and forging stock on CNC machines.
- Heat treatmentCarburising, quenching, tempering or nitriding to the route the original part uses.
- GrindingBores, spline seats and running faces are ground after heat treatment so distortion is removed.
- Lapping and superfinishingValve plates, shoe faces and block faces are lapped so the pair seals under pressure.
- InspectionDimensions, hardness and surface finish are recorded against the drawing on a sampling plan.
- Assembly and testComplete pumps are built, run in and tested for efficiency, leakage and noise before packing.
Quality Control
- Incoming material certificates are checked against the grade called for on the drawing.
- Hardness is measured after heat treatment on every batch and recorded on the batch card.
- Critical bores and running faces are gauged against the drawing tolerance, not against a sample part.
- Mating parts are matched as a set so the block, shoes and valve plate run in together.
- Rebuilt pumps are bench tested for volumetric efficiency, external leakage and sound level.
- Parts are cleaned, oiled and vacuum sealed so they arrive without surface rust.
Certifications and Documentation
Supplied on request with an order. We do not claim approvals we cannot evidence.
| Material certificate | Mill certificate for the steel grade used in the batch |
|---|---|
| Hardness report | Surface and core hardness readings after heat treatment |
| Dimensional report | Measured values for the critical features named on the drawing |
| Test bench report | Flow, efficiency, leakage and sound readings for a rebuilt pump |
| Packing list and photographs | Carton contents and photographs of the packed goods before shipment |
Customization Options
- Shaft and splineKeyed, straight or splined shaft ends built to your sample or drawing.
- Port and mountingFlange, thread and mounting pattern matched to the pump already on the machine.
- Seal materialNitrile, fluorocarbon or polyurethane for hot oil, fire resistant fluid or low temperature duty.
- Rotation and displacementLeft or right hand rotation and the displacement code your circuit was set up for.
- Marking and packingNeutral packing, your own carton artwork and your own part number laser marked on the part.
Comparison With Other Products
| Point | New Set | Replacing One Piston | Complete Rotary Group |
|---|---|---|---|
| Cost | Middle | Lowest | Highest |
| When it works | Several shoes worn or scored | One piece damaged and the rest measure good | Block and plate also worn |
| Balance | Set is matched | Depends on the wear of the rest | Set is matched |
| Risk of repeat failure | Low | Higher | Lowest |
Use Guide
- Measure shoe clearance on the old set to judge how far the pump has run.
- Inspect the swash plate face. A scored plate will destroy new shoes.
- Fit the retainer plate and ball guide as a matched pair with the set.
- Assemble wet with clean oil.
- Run in at low pressure and check case drain flow before full load.
Product Photographs
Related Products
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Frequently Asked Questions
Should I replace one piston or the whole set?
Replace the set unless the rest measure within limits. A new piston running with worn ones changes the load balance in the block.
Why do shoes fail?
Contaminated oil, running low on oil, and cavitation from a restricted suction line are the three usual causes.
Do you supply the retainer plate and ball guide?
Yes, and we recommend fitting them with a new piston set.
Are the sets weight matched?
Yes, sets are matched so the rotating group stays in balance.
Can you supply for a frame not listed?
Send the model code and photographs. We machine to drawing for frames outside the standard list.
Send Us the Model Code and We Will Quote
Tell us the model code stamped on the pump, the quantity and your delivery port. A quotation with lead time usually comes back within one working day.