Custom plain bearings
The demand for custom non-standard plain bearings is increasing. We can manufacture copper alloy materials to meet China’s national standards as well as the ASTM (UNS, SAE), EU, and JIS standards.
Bespoke plain bearings
viiplus collaborates with customers to find tailored solutions, offering plain bearings in various materials, sizes, tolerances, and designs.
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Committed to meeting tight deadlines without compromising on quality, we ensure reliable and efficient production timelines.
Versatility
Capable of handling both small-scale and high-volume orders, we provide seamless support for projects of any size. Additionally, we can develop custom copper alloy materials based on specific customer requirements and drawings.
Specialized in Custom Bearings & Bushings
Two bronze bushings can carry the same part number, run on the same machine and fail in the same year for opposite reasons. One was starved of grease. The other was asked to run dry at a sliding speed its solid lubricant could not follow. In both cases the alloy was sound; the specification was not. That is why this bronze bushings applications guide starts from the operating condition rather than the catalogue number. Across six industries the same three questions decide the answer: what load, what sliding speed, and what lubrication regime will actually be present on the day.
Custom Machined Bronze Parts & Bearings
What counts as a self-lubricating bronze bushing
Three product families are sold under one label, and mixing them up is the most common source of a wrong specification.
Cast and wrapped bronze — oil- or grease-lubricated. Solid bronze is a low-friction bearing material with good embeddability for dirt and the ability to take up small misalignment, but it is not self-lubricating. Deprived of grease, the wear rate climbs steeply and seizure follows. A plain cast bronze bushing and a wrapped bronze bushing are both in this family; both need a lubricant supply to give their published service life.
Graphite-plugged bronze. Plugs of graphite, sometimes graphite with additives, are pressed into a pattern of drilled holes in a cast bronze matrix. As the shaft moves, graphite smears onto the counterface and forms a transfer film. This is the family that genuinely runs without an oil supply, and it is the one whose published envelope is quoted across these pages.
PTFE-inlaid bronze. Solid lubricant in the form of PTFE-based inserts or a PTFE and graphite mixture, chosen where a lower coefficient of friction is needed and the temperature stays lower.
Oilless Bushing Material, Machining Parts
How the transfer film forms
The film is not magic. Graphite has a layered crystal structure, and shear takes place between the layers, so a thin film transfers onto the counterface within the first few hundred cycles. Once that film exists, contact is partly graphite on graphite rather than bronze on steel, and friction settles into the 0.08–0.20 range. Interrupt it — with a flooded oil supply that washes the film off, or a counterface too rough to hold it — and you are back to metal contact. The film needs a surface smooth enough to retain it and hard enough not to be abraded away, which is why counterface specification is part of the bearing design rather than an afterthought.
Application
Each of the six industries below fails in a characteristic way. Follow the one that matches your operating condition.
Marine and offshore: immersion zone before alloy
Stern tube bearings, rudder pintles and sea-water pump bushes see three different environments on the same hull: permanent immersion, the splash and tidal zone, and the salt-laden atmosphere above deck. Each has a different material answer, and treating them as one specification is why a bushing that survives ten years below the waterline can fail in eighteen months above it. Water-lubricated stern tube bearings, which run fast enough to build a water film, and dry-running hatch hinges are not the same duty and are not specified the same way. The full treatment is under marine and offshore bronze bushings.
Mining and heavy machinery: oscillation, not rotation
Excavator boom feet, dipper and bucket pins, crusher eccentrics and conveyor pivots almost never complete a full revolution. They oscillate through a small angle under high load, which means a hydrodynamic oil film never forms and the contact spends its life in the boundary regime. Add dust and slurry that convert grease into abrasive paste, plus remote sites where the greasing round is missed, and the bushing absorbs every one of those problems. See mining equipment bushings for excavators and crushers.
Hydraulic cylinders: side load, not thrust
In a cylinder, the bronze bushing in the gland carries the rod side load, keeps the rod concentric and holds the extrusion gap that the rod seal depends on. Sizing it is a projected-pressure calculation: force divided by rod diameter times bearing length. The confusion worth avoiding is that most published “bronze” wear ring data refers to bronze-filled PTFE or to sintered oil-impregnated bronze, not to machined cast bronze; those are three different products with three different envelopes. See hydraulic cylinder bronze bushings.
Wind power: long dwell, no access
Pitch and yaw bearings sit still for long periods and then move through a small angle under high load. The failure mode is fretting and false brinelling during dwell, not adhesive wear during movement. Whatever goes in has to hold up for years between inspections, with no routine greasing of the contact, which puts the emphasis on the solid-lubricant system rather than on the matrix strength. See wind turbine pitch and yaw bushings.
Steel plant and metallurgical: heat sets the ceiling
Continuous caster roll assemblies, ladle trunnions and furnace-area pivots run hot by default. Radiant heat and conduction from the product push the bushing toward the temperature ceiling of the matrix long before load becomes the limiting factor. High-temperature duty rules out lead-containing alloys, which are already out of the running at approximately 140 °C; above approximately 250 °C the answer is an aluminium bronze, because only a change of matrix raises the ceiling. Embedded graphite removes the lubrication limit, not the temperature limit. See steel mill bronze bearings.
Injection moulding: cycle rate and cleanliness
Toggle pivots, ejector plate guides and tie-bar bushings run at a high cycle rate with a short stroke, inside a machine where oil contamination of the product is unacceptable. The governing factors are the number of cycles per hour, the stroke length, and whether the pivot is greased or left dry — a dry pivot at a few thousand cycles an hour is a PV problem disguised as a wear problem. See injection molding machine bushings.
Material snapshot
Four grades cover most of the work described on these pages. The table below gives either the specification floor or a typical production figure for each property; the distinction matters, and it is explained underneath.
| Designation | Comparable UNS | Rm MPa | Rp0.2 MPa | A5 % | Hardness | Density g/cm³ | Typical duty |
|---|---|---|---|---|---|---|---|
| CuSn12-C CC483K / 2.1052 |
C90800 comparable to |
300 min. | 150 min. | 6 min. | 90 HBW min. | ≈8.8 | Sliding duty, shock, anti-seizure |
| CuSn7Zn4Pb7 (Rg7) CC493K / 2.1090 |
C93200 comparable to |
270 min. GC, DIN |
— | — | ≥70 HB typical |
≈8.9 | General purpose with regular greasing |
| CuAl10Fe5Ni5-C (NAB) CC333G |
C95800 / C95500 comparable to |
650 min. continuous, centrifugal, permanent mould 600 min. sand cast |
280 min. 250 min. |
13 min. | 150 HBW min. 140 HBW min. |
7.6–7.64 | Seawater, strength with corrosion resistance |
| CuZn25Al5 high-tensile brass, CC762S (comparable to) |
C86300 / SAE 430B comparable to |
780 typical |
— | — | 210 HB typical |
7.83 | High static load and impact |
Rm = tensile strength, Rp0.2 = 0.2 % proof strength, A5 = elongation after fracture. Values marked “min.” are specification floors bound to the test-bar or casting section size named in the governing standard; values marked “typical” are representative production figures. Where a designation from one standards system is placed beside a designation from another, the relationship is comparable to, or similar but not identical to, and independent verification is required before any substitution. Machinability ratings on the CDA scale (free-cutting brass = 100) are C90500 = 30, C93200 = 70, C93800 = 80 and C95800 = 50; no equivalent published rating exists for the aluminium bronzes, which are commonly described in published sources as comparable to steel of the same hardness. Figures compiled from published EN, DIN, ASTM, SAE and BS sources, cited here only as sources of published material property data.
Two points apply to every mechanical property table on this site, and both are regularly overlooked.
- Section size effect. Published values are bound to the test-bar or casting section size given in the governing specification. Large sections generally show lower strength and hardness, particularly in yield. The outer skin of a casting is harder than its core, so a component machined heavily from one face no longer retains the as-cast surface values.
- “min.” is not an expected value. Mechanical properties in material standards are specification floors rather than production targets. Production material usually sits well above them, and no design should be built on the minimum figure.
The four numbers that decide the path
Four quantities, taken together, will usually narrow the choice to two candidates. Taken one at a time, each of them will mislead you.
1. Unit load
Divide the force by the projected bearing area — diameter times bearing length for a plain cylindrical bushing — and compare the result with the allowable surface pressure for the lubrication regime you will actually have. This is where undersized bushings are caught: the alloy gets blamed, when the real problem is that the bearing is too short for the load it carries.
2. Sliding speed, and PV
Speed alone rarely kills a bushing. PV — unit load multiplied by sliding speed — is the proxy for the rate of heat generation at the contact, and heat is what degrades both the transfer film and the matrix. A high load at 0.05 m/s can be a comfortable duty; the same load at 2 m/s is a different machine.
3. Temperature
This is really two questions: the bulk temperature arriving from the process, and the flash temperature at the contact itself. The matrix sets the ceiling, not the grease. Lead melts at 327 °C. Published maximum mechanical service temperatures are approximately 140 °C for C93700-class leaded tin bronze, approximately 250 °C for CuSn12 and approximately 260 °C for C86300; the incipient melting point of C93800 is 316 °C. Above approximately 250 °C the answer is an aluminium bronze, because only a change of matrix raises the ceiling; a tin bronze with embedded solid lubricant answers a different question — it is for a position whose temperature already sits inside the tin bronze ceiling but where no grease or oil supply can be maintained. Embedded graphite removes the lubrication limit, not the temperature limit.
4. Environment and contamination
Dust and slurry turn grease into lapping compound. Salt spray and immersion change the corrosion question completely. Wash-down removes whatever the greasing schedule added. And whether the duty is continuous or intermittent changes the answer to all three of the numbers above: an intermittent peak is a different design case from a continuous load of the same value.
Graphite-plugged bronze — published engineering envelope (dry running)
- Solid-lubricant coverage of the sliding surface: 20–30 % (some published standards specify 25–35 %)
- Plug diameter: φ3–10 mm
- Allowable surface pressure, dry running: ≈100 N/mm² (aluminium-bronze matrix up to 120)
- Sliding speed, dry running: ≤0.5 m/s
- PV ceiling, dry running: ≈1.0–2.5 N/mm²·m/s (oil-lubricated up to 5.0)
- Counterface hardness: ≥40–45 HRC, surface finish Ra ≤0.8 µm
- Coefficient of friction, dry: 0.08–0.20
These figures apply to dry running. Where a PV or load value is quoted, the lubrication regime — dry, boundary or full-fluid — and whether the duty is continuous or intermittent must be stated alongside it.
Send us the four numbers. Load, sliding speed, temperature and lubrication regime — with a note on whether the duty is continuous or intermittent — are enough for us to come back with a candidate grade, a wall thickness and a plug layout.
Work through the PV calculation first if you do not have a figure yet.
type of Custom Bearings & Bushings, Flanged Bearings, Custom Oilless Bronze Bushings, Custom Sliding Bearing
Custom Bearings & Bushings Materials & Alloys We Machine
Material Selection
Bronze Alloy Composition
Casting
Centrifugal casting, continuous casting
Machining
Precision Machining
Quality Inspection
Material Testing, Surface Inspection
