An oilless bushing is a plain bearing that carries its own lubricant inside the part, so it runs without an external oil or grease system. Instead of a lubrication line or periodic re-greasing, the bearing holds a solid or impregnated lubricant in reservoirs built into the sliding surface. This page explains the lubrication mechanism, the cast bronze base material, the graphite-plugged construction, how to choose a build, and the alloy grades and fits involved.
What “Oilless” Means
An oilless bushing supplies lubrication from within. Solid lubricant sits at or near the bore where the shaft runs; as the shaft moves, a thin solid film transfers onto the mating surface and keeps friction low without a liquid oil film. “Oilless” and “self-lubricating” describe the same family of solid-lubricant bearings — this site uses “self-lubricating” as the technical term. Service needs still depend on load, speed, contamination, and duty cycle, which vary by application.
Cast Bronze: The Base Material
Most oilless bushings in this catalog are built from cast bronze — a continuous-cast or sand-cast blank that is then machined to the finished bore, OD, and length. Continuous casting produces a dense, uniform grain with few voids, which machines cleanly and carries load well; sand casting suits larger diameters, low-volume discs, and washers. Cast bronze is the usual base for graphite-plugged (JDB-style) oilless bushings because the solid matrix both supports the shaft load and physically holds the embedded graphite plugs. The alloy is chosen for the duty: aluminum and nickel-aluminum bronzes for strength and corrosion resistance, manganese bronze for heavy slow pivots, and tin/leaded tin bronzes where machinability and anti-friction behavior matter.
How a Cast Bronze Oilless Bushing Carries Lubricant
The oilless bushing covered here is a cast bronze part with graphite (or a graphite-based) plugs set into pockets on the bore and sometimes the flange face. As the shaft turns, the plugs transfer a thin solid film to the shaft, keeping friction low without a liquid oil film. The cast bronze matrix does the structural work; the plugs do the lubrication. Plug patterns are laid out to clear the loaded zone — common arrangements are a grid, a perimeter ring, or a figure-eight groove.
Dimensions and Fit
Cast bronze oilless bushings follow the same dimensional standards as other solid plain bushes. Wrapped (multi-layer) types are dimensioned by ISO 3547-1:2018; solid copper-alloy bushes by ISO 4379 (with DIN 1850 as the long-standing equivalent); GB/T 2889 covers plain-bearing vocabulary. A common radial fit starts at an H7 bore with an e7–e8 shaft. For graphite-plugged builds, the plug layout must clear the loaded zone without removing too much wall material.
| Alloy family (examples) | Graphite-plugged cast bronze | Notes |
|---|---|---|
| Aluminum bronze (C95400, C95500) | Suitable | High strength and corrosion resistance; common for marine, outdoor, and heavy graphite-plugged duty. |
| Nickel aluminum bronze (C63000) | Suitable | Seawater-resisting corrosion behavior for submerged or coastal service. |
| Manganese bronze (C86300) | Suitable | High mechanical strength for heavy, slow oscillating pivots. |
| Tin / leaded tin bronze (C93200, C93700, C93800, C94300) | Suitable | Good machinability and anti-friction behavior; leaded grades are not described as lead-free. |
| Build | Lubrication mechanism | Recommended for | Note |
|---|---|---|---|
| Graphite-plugged cast bronze | Solid graphite plugs embedded in a machined cast bronze matrix lay down a dry film | Heavy, slow, oscillating, dirty, or corrosive service | Primary construction in this catalog; supports high load |
| Oil-impregnated sintered bronze | Porous preform soaked in oil bleeds lubricant to the surface | Lighter, faster, cleaner rotating duty | Different process from cast bronze; suits lower load |
| PTFE / polymer-lined | Dry-running polymer face bonded to a backing | Oil-trace-free duty at moderate load | Secondary option; considered where a polymer face is acceptable |
| Duty | Recommended build |
|---|---|
| Heavy, slow, oscillating loads in dirty or wet service | Cast bronze with graphite plugs |
| Corrosive or submerged service | Low-lead aluminum or nickel-aluminum bronze with graphite plugs |
| Oil trace unacceptable but load is moderate | PTFE-/polymer-faced variant (secondary option) |
| Lighter, faster, cleaner rotating duty | Oil-impregnated sintered build may be considered instead |
Selection checklist
- Pick the construction from duty: cast bronze with graphite plugs for heavy / low-speed / dirty or corrosive service (lighter, faster, cleaner duty may suit a sintered build instead).
- Choose alloy by environment and by whether leaded grades are acceptable.
- Choose geometry — sleeve, flanged, or thrust — from the load direction.
- Set bore/shaft fit (e.g., H7/e7–e8); for graphite-plugged builds, confirm plug layout clears the loaded zone.
- Validate against the actual load, speed, and environment rather than a generic rating.
Where a Cast Bronze Oilless Build Is the Right Choice
Cast bronze graphite-plugged construction is selected when the absence of an external oil supply is the deciding factor and the duty is heavy, slow, or contaminated:
- Grease points that are hard to reach — enclosed, sealed, or remote pivots where a lubrication line or re-greasing schedule is impractical.
- Contaminated or dirty service — dust, slurry, or washdown environments where a liquid oil film would break down; a solid film keeps friction low without an oil bath.
- Sealed or lifetime-lubricated designs — assemblies intended to run with no planned maintenance access.
- Corrosive or outdoor service — cast aluminum or nickel-aluminum bronze carries the load and resists the environment while the plugs handle lubrication.
- Long unattended or remote installations — where a missed re-lubrication is costly or unsafe.
Fitness and exercise equipment is covered in the gym equipment bearings guide. For a specific application example, see Oilless Bushings for Blow Molding.
Frequently Asked Questions
Are oilless bushings the same as self-lubricating bushings?
Yes — “oilless” and “self-lubricating” refer to the same family of plain bearings that carry their own solid lubricant and run without an external oil supply. This site uses “self-lubricating” as the preferred technical term.
What is the difference between oilless and graphite bronze bushings?
The oilless bushings covered in this catalog are cast bronze with embedded graphite plugs (a JDB-style build). “Oilless” is the broader category that also spans other solid-lubricant routes such as oil-impregnated sintered bronze or polymer-lined backs; this catalog focuses on the cast bronze graphite-plugged construction. For the material build, see the graphite bronze bushings page.
Can an oilless bushing replace a greased bronze bushing directly?
Often it is a sound design choice where a lubrication point is undesirable, but it is not an automatic drop-in. The load, speed, and fit envelope must be checked against the oilless construction’s capabilities before substitution.
Is an oilless bushing the same as a wrapped (rolled) bearing?
No. A wrapped bush (dimensioned by ISO 3547-1) is a thin-walled, multi-layer bearing often pre-lubricated or lined with a polymer; a cast bronze oilless bushing carries its lubricant in solid graphite plugs set into a solid machined part. The two describe different construction philosophies.
Do oilless bushings need any maintenance?
They remove the need for a continuous external oil supply, but service interval depends on load, speed, contamination, and duty cycle. Specific intervals should come from the supplier specification, not a generic claim.
