Plain Bearing Bush: Types, Materials and How to Choose
Maintenance-free Plain Bearings
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On-Demand Manufacturing of Plain bearing Bush
A bearing bush — also called a plain bush, sleeve bearing or bushing — is the simplest sliding bearing there is: a cylinder pressed into a bore, through which a shaft runs. Where rolling bearings roll, a bush slides, and that one difference buys it lower cost, smaller size, higher load capacity per volume and tolerance of shock and misalignment — at the price of needing the right material, fit and lubrication. This page is the entry point to the whole class: the five constructions, how each behaves, and the short decision path that narrows a duty to one design.
What a bearing bush is (and the names for it)
“Bearing bush”, “plain bush”, “sleeve bearing”, “bushing” and “journal bearing” all describe the same thing viewed from different angles:
- Bush / bushing — the component; a sleeve that lines a housing bore. A “bushing” is often the ready-to-fit part, a “bush” the plain cylindrical insert.
- Sleeve bearing — the same part named for its shape; a full (unsplit) or split (wrapped) cylinder.
- Plain bearing — the class, opposed to rolling bearings (balls and rollers) and opposed to fluid-film bearings run purely hydrodynamically.
- Journal bearing — the engineering term when the loaded shaft runs inside the bush and the load acts through the shaft.
A bush works by sliding contact. Whether it survives depends on the PV duty — pressure on the projected area times sliding speed — and on how that duty is lubricated. Two bushes of identical size from the same catalogue can differ enormously in life if one is greased and the other is expected to run dry.
The five bush constructions
Every plain bearing bush is one of five constructions, and the construction — not the brand — decides what the bush can do:
| Construction | How it is made | Typical wall | Where it wins |
|---|---|---|---|
| Solid / cast | Bronze, brass or iron machined from cast bar or forging | thick — any | Heavy loads, large bores, custom lengths, wear plates, gears and nuts |
| Wrapped / rolled | Strip rolled into a split sleeve (CuSn8, bi-metal) | ~0.75–3 mm | High-volume thin-wall bushes, standard bores, press-fit into steel housings |
| Sintered / oil-impregnated | Powder pressed and sintered, oil-vacuum impregnated (SAE 841) | ~1.5–4 mm | Small motors, appliances, intermittent duty with no re-lubrication |
| Bi-metal / composite | Steel back + bronze interlayer + polymer or PTFE liner | ~1–3 mm | Dry-running, soft or plated shafts, wide temperature range, low maintenance |
| Polymer (solid plastic) | Injection moulded or machined PEEK / POM / PA | any | Corrosion-free, lubricant-free, low load, high-volume parts |
Each construction has its own depth page or family in the links below. The rest of this page is the overview and the selection logic that routes you to the right one.
Industries that use bushes
Plain bearing bushes are specified by the machine, not the industry. Every sector has its characteristic duty — and its own page of solved examples:
Marine & offshore
Stern tubes, rudder stock, seawater pumps
Ports, cranes & material handling
Sheave pins, trunnions, heavy pivots
Hydropower & hydraulic structures
Gate hinges, turbines, valves — often water-lubricated
Mining & construction
Track, excavator, crusher and mill bushings
Steel & metallurgy
Rolling mill nuts, furnace rollers, heavy slides
Food, beverage & packaging
Wash-down and food-contact — material compliance matters
Pumps, valves & fluid power
Bushings in fluid, valves, cylinders
Automotive
High-volume wrapped and composite bushes
| Mode | Oil / grease supply | Typical construction | Duty ceiling |
|---|---|---|---|
| Hydrodynamic film | Continuous, pressurised or self-pumping wedge | Cast bronze or bi-metal with grooves | Highest PV; speed-limited |
| Boundary lubrication | Grease at intervals through grooves | Cast bronze (C93200/C93700), wrapped CuSn8 | Moderate PV |
| Oil-impregnated (self) | None — oil stored in sintered pores | Sintered bronze (SAE 841) | Low PV, intermittent |
| Solid lubricant plugs | None — graphite/MoS₂ plugs | Plugged cast bronze (JDB-type) | High load, low speed, maintenance-free |
| Dry / liner film | None — PTFE or polymer transfer film | Bi-metal PTFE composite, polymer | Low–moderate PV, wide temperature |
The lubrication method is the single largest variable in a bush’s performance. An enquiry that does not state how the bush is lubricated cannot be answered with a meaningful load rating — and most wrong-bush failures trace back to a mismatch here, not to the material’s chemistry.
A short decision path
Choosing a bush is mostly eliminating, not searching. Work down these questions in order:
- Can the bush be greased or oiled, or must it run maintenance-free? If it must be maintenance-free, go straight to self-lubricating bearings (plugs, sintered oil, or PTFE liner) and skip the plain bronze greased route.
- What is the PV duty? High load with low speed suits cast or plugged bronze. Low load with high speed suits composite or polymer. Both high load and high speed with continuous oil suits a grooved hydrodynamic bush — a specialist design, not a catalogue sleeve.
- What is the shaft made of and how hard is it? Soft, unhardened or plated shafts need a soft, embeddable lining (leaded tin bronze, composite liner, polymer) that will not score them. Hardened ground shafts tolerate the harder, stronger materials.
- What is the environment? Water, seawater, chemicals or wash-down push you toward corrosion-capable grades (nickel aluminium bronze, stainless-backed composite, polymer) and away from plain carbon-steel-backed and leaded-grease options.
- Volume and geometry? High-volume thin-wall standard bores favour wrapped or sintered catalogue bushes; heavy custom bores and wear plates favour solid cast machined parts.
The usual failure is a material, not a size, problem
When a bush fails early, engineers often blame the fit and go one size up. In practice the dominant causes are a lubrication mismatch (greased vs. dry), a shaft too soft for a hard bushing, or contamination that a leaded or plugged material would have embedded. Read plain bearing materials for the failure-mode view of selection before resizing.
FAQ
- What is the difference between a bearing bush and a bushing?
- Practically none. “Bush” and “bushing” both name the cylindrical sliding bearing that lines a bore, the split version of which is also called a “bushing” or “bush”. “Bearing bush” usually implies the product type (a bush that works as a bearing), “bushing” the component in a housing. In engineering terms they are synonyms; what matters is specifying bore, outside diameter, fit and material.
- Is a sleeve bearing the same as a plain bearing?
- A sleeve bearing is one shape of plain bearing — a cylinder, unsplit or split, in which a shaft slides or rotates. Plain bearing is the wider class that also includes thrust washers, wear plates, slide pads and spherical seats. Sleeve bearing and plain bearing bush are used interchangeably for the cylindrical form.
- How long does a bearing bush last?
- There is no single answer: life is set by PV duty, lubrication, shaft finish and contamination. A correctly sized, properly greased bronze bush can outlast the machine; a maintenance-free composite is designed for a stated life at a stated PV. Real life is predicted from the wear coefficient and duty, not from a generic number — ask for the envelope that matches your duty cycle.
- Should I choose bronze, graphite-plugged, or PTFE composite?
- By maintenance and shaft first. If grease is impossible or unwanted, choose maintenance-free: graphite-plugged for heavy slow loads, PTFE composite or polymer for lighter, faster or corrosion-heavy duty. If greasing is acceptable, a plain bronze bush (leaded tin bronze on a hardened shaft, aluminium bronze for heavy duty) is usually the most economical answer.
- Why did my bushing wear the shaft?
- Most shaft-scoring comes from hard bushing material running against a soft or rough shaft, from abrasive contamination, or from a dry start that removed the transfer film. Fix by choosing a soft, embeddable lining for soft shafts (leaded or composite), improving the shaft finish, or adding lubrication/plugs — in that order of likelihood.
What to specify when you buy
- Duty: load (N or MPa on projected area), speed, motion type (rotary / oscillating / linear) and duty cycle.
- Lubrication state: greased / oiled / dry / initial-grease-only — state it explicitly.
- Shaft: material, hardness, surface finish (aim Ra 0.4–1.6 µm for most sliding surfaces).
- Environment: temperature range, moisture, chemicals, wash-down, contamination.
- Geometry: bore and outside diameter with fit class (typically H7 housing / recommended clearance), length, and any groove, flange or oil-hole features.
- Material: name the standard and grade (e.g. C93200 per ASTM B505, SAE 841, CuSn8 per DIN 1494) — not just a trade name.
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