Tapered Bronze Bushings: Specifications, Material Grades and Custom Manufacturing
A tapered bronze bushing is a cast bronze sliding bearing whose bore or outside diameter is machined to a shallow cone instead of a cylinder. The cone lets the bushing self-centre in a housing, hold a controlled running clearance, and be drawn up or released during assembly and overhaul without a press fit. This page covers internal versus external taper, one-piece versus split construction, the dimensional parameters that need fixing before manufacture, material grades, and the information required to request a quotation.
What a tapered bronze bushing is
A tapered bronze bushing is a cylindrical bearing component with a conical rather than a parallel wall. In service it carries load between a shaft and a housing, and the taper governs how the part seats, centres and releases. Tapers are specified either on the bore (internal taper) or on the outside diameter (external taper), and the choice follows the mating geometry rather than convention.
Bronze is used for this part because it combines load capacity with conformability and embeddability. A bronze bearing surface tolerates a degree of misalignment, and it allows small contaminant particles to become embedded in the bearing wall instead of scoring the shaft. Where lubrication cannot be maintained reliably, the same tapered geometry can be produced with graphite plugs or with machined lubricant grooves.
Dimensional range and tolerances
Tapered bushings are normally made to drawing, so the table below sets out the parameters that need to be fixed before manufacture begins.
| Parameter | Range or value | Notes |
|---|---|---|
| Inside diameter (bore) | 10 – 1,000 mm | State whether quoted at the large or small end |
| Outside diameter | 15 – 1,200 mm | For external taper, quote the large end |
| Length | 10 – 1,000 mm | |
| Wall thickness | 3 – 150 mm | Thin walls constrain the casting route and should be flagged early |
| Taper ratio | To drawing | State whether measured on diameter or radius — the difference is a factor of two |
| Bore tolerance | H7 | ISO 286. H6 available where closer control is needed; confirm against the fit required |
| OD tolerance | p6 | ISO 286. s6 for heavier interference; selected against housing material and wall |
| Running clearance | e7 or f7 | ISO 286. Final value depends on shaft diameter, speed, temperature rise and grade |
| Surface finish, bore | Ra 0.8 – 3.2 µm | Finer finish at the lower end for higher speed or closer clearance |
| Roundness / concentricity | To ISO 1101 | Verified by CMM or roundness instrument |
Two points cause most fitting problems. First, always state whether the taper ratio is measured on diameter or on radius. Second, state which end the dimension applies to — a taper dimension quoted at the large end describes a different part from one quoted at the small end.
Material grades and mechanical properties
Grade selection should follow the load case rather than habit. The table below gives typical values for the three grades most frequently used for tapered bushings. Values are indicative and must be confirmed against the governing standard and the mill certificate for the supplied condition and product form.
| Property | C93200 (SAE 660) | C95400 aluminium bronze | C86300 manganese bronze |
|---|---|---|---|
| Tensile strength (min) | 241 MPa (35 ksi) | 586 MPa (85 ksi) | 758 MPa (110 ksi) |
| Yield strength (min) | 138 MPa (20 ksi) | 221 MPa (32 ksi) | 427 MPa (62 ksi) |
| Elongation (min) | 10% | 12% | 14% |
| Hardness (typical) | 70 HB | 170 HB | >220 HB |
| Density | 8.91 g/cm³ | 7.45 g/cm³ | 7.83 g/cm³ |
| Lubrication demand | High — continuous or frequent | Low — intermittent, with self-lubricating options | Medium — reliable lubrication required |
| Corrosion resistance | Fair to good (general) | Excellent, including seawater | Good in marine environments |
| Principal limitation | Dependent on lubrication; contains lead | More demanding to machine; higher material cost | Dependent on lubrication; more demanding to machine |
C93200 (SAE 660) is a leaded tin bronze with good conformability and embeddability, used where lubrication is reliable and the part is accessible for replacement. C95400 offers higher strength and corrosion resistance and is selected for heavier loads and aggressive environments. C86300 has the highest load capacity of the three and is used for slow, heavily loaded applications, with the caveat that the counterface hardness and lubrication regime need to be reviewed together with the grade.
Where access for lubrication is limited or the duty is intermittent, the tapered geometry can be combined with graphite plugs or with machined groove patterns. See graphite bronze groove bushings and the groove types used for lubricant distribution.
How to select a tapered bronze bushing
Wear is not a single material property. It results from the interaction of the following factors, and a specification that omits any of them cannot be quoted reliably.
| Decision factor | What to establish | Why it matters |
|---|---|---|
| Load | Magnitude and direction (radial, axial or combined); static or dynamic; shock or reversing | Sets the grade and the wall thickness |
| Sliding speed and duty | Surface speed; continuous rotation, oscillation or intermittent motion; start-stop frequency | Determines the PV condition and whether the grade is suitable |
| Lubrication regime | Flooded, grease, boundary, or none | Decides between standard bronze and graphite-plugged construction |
| Counterface | Shaft material, hardness, surface finish | Harder grades require a harder, finer-finished shaft |
| Environment | Operating temperature; contamination; corrosive exposure | Drives grade selection and seal design |
| Assembly and overhaul | How the part is fitted and removed; expected replacement frequency | Determines taper direction, split or one-piece, and clearance |
For a fuller treatment of the trade-offs between grades, including where high-strength nickel aluminium bronze is justified, see our bearing selection guide.
Manufacturing route and inspection
Tapered bronze bushings are produced by centrifugal casting or sand casting, followed by CNC machining of the taper, bore and faces. Centrifugal casting gives a denser structure with fewer defects and suits annular parts; sand casting allows larger sections and more complex external features.
Machining the taper requires the cone to be generated against the mating angle rather than approximated, and the two parts are checked together where the application requires matched seating. Inspection typically covers chemical composition against the specified standard, hardness, dimensional verification of the taper and bore, and non-destructive examination where the section thickness or duty warrants it.
Material is supplied with a mill certificate confirming composition and mechanical properties to ASTM B505 / B271 or EN 1982, as specified on the order.
Frequently asked questions
What is the difference between a tapered bronze bushing and a Taper-Lock bush?
A tapered bronze bushing is a sliding bearing that carries load between a shaft and a housing. A Taper-Lock bush is a locking device that clamps a pulley, sprocket or coupling onto a shaft in power transmission. They differ in material, function and how they are specified: Taper-Lock bushes are selected by series code, while tapered bronze bushings are made to drawing.
Should I specify an internal or an external taper?
It follows the mating geometry. Use an internal taper where the shaft or spigot is tapered and the bushing must seat onto it. Use an external taper where the housing bore carries the taper. If both parts are available for redesign, the decision usually turns on which component is easier to machine accurately and which one needs to be released at overhaul.
When is a split tapered bushing necessary?
Where the shaft cannot be withdrawn axially, where the housing is too large to install a one-piece part, or where the bushing has to be replaced without dismantling the surrounding assembly. Split construction allows replacement in situ, at the cost of a joint line that must be located and matched correctly.
What tolerance should I specify?
It depends on the fit. Housing bores are commonly machined to an H7 tolerance with the bushing outside diameter produced to an interference fit such as p6 or s6, while the running clearance is controlled on the bore. The appropriate values depend on shaft diameter, operating temperature and the materials involved, and should be confirmed against the application.
Which grade should I use for a heavily loaded, slow-moving joint?
C86300 manganese bronze offers the highest load capacity of the three grades listed and is often considered for slow, heavily loaded applications. It requires reliable lubrication and a sufficiently hard shaft, so the counterface specification should be reviewed at the same time. Where corrosion resistance is the dominant requirement, C95400 is usually the starting point.
Can a tapered bushing run without lubrication?
Yes, with the right construction. Standard bronze grades depend on a lubricant film. Where lubrication cannot be maintained, the bushing can be supplied with graphite plugs or with machined grooves that distribute solid lubricant across the bearing surface. Suitability depends on load, speed and temperature, so the duty cycle needs to be supplied with the enquiry.
Typical applications
Tapered bronze bushings appear where a pivoting or oscillating joint carries high load at low speed, and where the part has to be removable for overhaul. Common applications include:
- Construction machinery — pivot points on excavator and bulldozer linkages, boom and arm joints
- Mining equipment — crusher and screen pivots, conveyor and haulage assemblies
- Material handling — conveyor drive and idler assemblies, hoist and winch bearings
- Hydraulic structures — gate trunnions and hinge bearings, where service intervals are long and access is difficult
- Marine — deck machinery, rudder and steering gear bearings in contact with seawater
- Power generation equipment — turbine auxiliary bearings, valve and linkage bushings
Reviewing a tapered bushing specification, or comparing grades for an existing assembly?
Our bronze bushings page covers the full range of standard and custom configurations, or send a drawing and duty data for a quotation.
