Oilless Bearings services
Construction Bearing Materials for Excavators, Cranes and Dozers
Nearly every pivot on a piece of earthmoving equipment runs on a plain bearing rather than a rolling bearing. The swing ring of an excavator, the boom foot pin of a crane, the bucket linkage of a backhoe loader and the articulation joint of a dump truck all carry high static load through a small oscillating angle, usually with sand and water inside the joint. This page maps the bronze alloys we machine for those positions to the loads, speeds and temperatures they meet, and sets out the cases where a hardened steel bush or a rolling bearing is the more sensible replacement.
Solutions
What the term construction bearing covers here
In this context a construction bearing means the plain bearing elements built into the machine structure:
- Sleeve and flanged bushings pressed into a linkage boss, a cylinder eye or a pivot housing.
- Thrust washers taking axial load against a pivot face, for example at the side of a boom boss.
- Wear plates and slide strips in telescopic boom sections, outrigger beams, track frames and guide channels.
- Lined and spherical joints where the articulation angle is large or the load path changes direction.
What all of these share is oscillation rather than full rotation. Surface speed is usually below 0.1 m/s (4 in/s), contact pressure on the projected area often falls in the 20–60 MPa (2,900–8,700 psi) band, and the joint may sit under load without moving for long periods. Some points are greased through a nipple on a service interval; others are sealed for life or simply never get greased once the machine is in the field. Alloy choice follows from those three facts rather than from a catalogue ranking. More background on the machine types involved is on the construction machinery application page.
Material mapped to duty
The table below is the one most buyers start from: what each alloy provides, the duty it suits, and the position on the machine where we most often supply it. Mechanical values are typical for the forms we stock and should be confirmed against the mill certificate for the heat supplied.
| Alloy | What the alloy gives | Duty it suits | Typical position on the machine |
|---|---|---|---|
| CuSn8P phosphor bronze | High wear and fatigue resistance; work-hardens under load; holds a good surface where grease is present. Typical tensile 400–550 MPa, hardness 90–140 HB. | High load with oscillation, greased or occasionally greased; moderate shock. | Crane boom pivots, wrapped bushes in link bosses, boom foot pins. See phosphor bronze bushings. |
| CuAl10Fe3 aluminum bronze | Corrosion resistance in salt water and process water, strength retained at elevated temperature, good resistance to abrasive wear. Typical tensile 550–680 MPa, hardness 130–180 HB. | Abrasive or coastal sites, high load, elevated temperature from friction. | Excavator swing ring wear rings, dredger and coastal-site pivots. |
| CuSn12 tin bronze | High hardness for a tin bronze with good thermal conductivity, which helps move friction heat out of the contact. Typical tensile 240–320 MPa, hardness 80–110 HB. | Abrasion-dominated wear where embeddability matters less than hardness. | Bulldozer track link and idler bushes, slide strips in track frames. |
| CuPb15Sn8 lead bronze | Lead phase gives self-lubricating behaviour when the oil film breaks down; tolerates dirty joints. Typical tensile 150–220 MPa, hardness 45–70 HB. | Low to moderate load, marginal or irregular lubrication, low-maintenance service. | Backhoe loader bucket hinges, bulldozer track link bushes, linkage pivots that are greased rarely. |
| CuZn25Al6Mn4 with graphite plugs | High-strength manganese brass carrying embedded graphite; runs without grease. Typical tensile 600–750 MPa, hardness 180–230 HB. | High load, dry or barely lubricated, wide temperature swing. | Hydraulic cylinder rod guides and piston wear bands, articulated dump truck joints. |
| Steel-backed bronze with PTFE liner | Steel backing carries the structural load, the PTFE-based liner sets friction and wear. Liner suppliers commonly quote dynamic ratings in the 50–120 MPa band at low speed — the liner data sheet governs. | Low friction at small oscillation angles, high-precision joints, sealed-for-life assemblies. | Articulation joints, spherical ends, precision linkages where stick-slip has to be avoided. |
Designations such as CuSn8P, CuAl10Fe3 and CuPb15Sn8 are EN-style material shorthand and cross to UNS numbers with some spread in composition limits. Where a drawing gives only the EN-style name, we confirm the standard revision before quoting.
Maintenance & Longevity
Here, you can find a number of fitting offers for your construction-machinery bearing
For information about the full range of offers, and to find a specific solution for your needs, please contact us.
Load, speed and temperature by joint
The same alloy behaves differently in a swing ring and in a bucket hinge, because the load pattern and the lubrication regime differ. This table gives the duty we design against for the six positions most often asked about.
| Joint | Motion and speed | Load pattern | Temperature, typical | Alloy usually supplied | Note |
|---|---|---|---|---|---|
| Excavator swing ring / slew ring | Slow rotation to oscillation, roughly 0.5–5 rpm | Combined radial and axial load with shock from digging | −20 to +60 °C (−4 to +140 °F) ambient, plus friction heat at the race | CuAl10Fe3, or CuSn8P where greasing is reliable | Counterface hardness and flatness decide service life; check race condition before ordering only a bushing. |
| Crane boom pivot and boom foot pin | Oscillation below about ±30°, surface speed under 0.05 m/s (2 in/s) | High static load, infrequent movement, brinelling risk | −20 to +80 °C (−4 to +176 °F) | CuSn8P wrapped, or CuZn25Al6Mn4 with graphite where greasing is unreliable | Pressure on the projected area matters more than PV; verify against the pin diameter. |
| Bulldozer track link and idler | Small oscillation per cycle plus sliding in abrasive slurry | High shock, abrasion-dominated | −30 to +80 °C (−22 to +176 °F) | CuSn12, CuPb15Sn8 | Hardness and contamination resistance decide the choice; grease retention is poor, so self-lubricating grades earn their cost. |
| Backhoe loader bucket hinge | Full cycles, several per minute | Moderate shock, constant contamination with soil and water | −20 to +70 °C (−4 to +158 °F) | CuPb15Sn8, or graphite-plugged CuZn25Al6Mn4 | Sealing the joint often extends life more than changing the alloy. |
| Hydraulic cylinder rod guide and piston | Reciprocating sliding up to about 0.5 m/s (20 in/s) | Side load from misalignment, pressure from rod load | Oil temperature −40 to +120 °C (−40 to +248 °F) | CuZn25Al6Mn4 with graphite, or steel-backed bronze with PTFE | The rod is the counterface; a scored rod will destroy any bronze guide. |
| Articulated dump truck joint | Low-angle oscillation with continuous vibration | High shock, reversing load | −40 to +80 °C (−40 to +176 °F) | Graphite-plugged high-strength brass, or steel-backed lined bearing | Machines that articulate under full load need the plug pattern reviewed, not just the alloy. |
Two numbers help shortlist. The PV value — contact pressure in MPa multiplied by sliding speed in m/s — is a rough ordering tool: greased bronze in these joints commonly runs below about 1.0 MPa·m/min in sustained service, while dry-running graphite-plugged bronze tolerates more because the graphite supplies the film. The second number is the temperature window. The −40 °C to +300 °C (−40 °F to +572 °F) band often quoted for graphite-plugged high-strength brass is a typical working window for the bushing material alone; the usable limit in a real joint depends on the alloy, the graphite grade, whether any grease is present, and on the housing and shaft materials. At the cold end the housing contracts and running clearance closes; at the hot end graphite oxidises progressively above roughly 400 °C (750 °F) and the bronze loses strength.
Where self-lubrication is worth paying for
Graphite-plugged bronze costs more per part than a plain bronze bushing of the same size. It pays back on the joints that a greasing route never reaches: sealed articulation bearings, pivot points at the top of a boom, and any position where a missed service interval leads to a seized pin. Plug layout is a design step, not a finishing detail — coverage is normally 20–30% of the loaded area, arranged so that every point on the counterface passes over plugs during the working stroke. The plug size and layout calculation walks through the arithmetic, and the graphite-plugged bushing range shows the usual forms.
Where the joint has a grease nipple and the service schedule is actually followed, a plain phosphor or leaded bronze bushing with machined grease grooves will give comparable life at lower unit cost. Specifying graphite plugs on a well-greased, lightly loaded joint buys capability the application does not use.
Steel-backed and lined constructions suit a different problem: low friction at very small oscillation angles, where stick-slip would show up as jerky boom movement. See the steel and copper inlaid bearing construction, and the wear plate and liner forms used in telescopic booms and guide channels.
Fits, clearance and installation
Most premature failures on construction plant are fitting failures rather than material failures. The checks that matter:
- Housing and press fit. A housing bored to H7 with the bushing outside diameter left to give an interference fit is the usual arrangement. After pressing, the bore closes by roughly 0.5–0.8 times the interference, so either finish the bore after installation or size the blank to allow for it.
- Running clearance. Start from 0.1–0.2% of shaft diameter: on a 100 mm (3.94 in) pin that is 0.10–0.20 mm (0.004–0.008 in). Add allowance for thermal growth — a 100 mm steel pin rising 100 K grows by about 0.12 mm — and for housing contraction at the cold end of the range.
- Counterface. For aluminum bronze and graphite-plugged high-strength brass, ask for shaft hardness above about 250–300 HB and a finish of Ra 0.8 µm (32 µin) or better. A soft pin will be scored rather than polished.
- Measurement. Measure the bore at 20 °C (68 °F) on the same equipment used for final inspection; the method is set out in reading and measuring bearing tolerance.
- Assembly. Press with a mandrel that bears on the full end face, never drive on a flange. Line up the grease hole before pressing, and check that the bushing has not closed below the clearance figure once it is seated.
- Thrust faces. Where the joint takes axial load, check that the washer or flange face is supported over its full area; a washer sitting on a machined step smaller than its face will dish.
When a construction bearing should be something else
Bronze is not the automatic answer. These conditions point elsewhere:
- Very high impact or shock loading. If the joint sees repeated hammering — a breaker attachment mount is the usual example — bronze will brinell and loosen in the housing. A hardened steel bush or a rolling bearing handles the load case better.
- Continuous rotation. Above roughly 1 m/s (40 in/s) surface speed, a rolling bearing runs cooler and uses less power. Plain bronze is for oscillation, not for sustained rotation.
- A reliable greasing route exists and loads are moderate. A plain tin or phosphor bronze bushing with grease grooves costs less than a graphite-plugged bushing and will last as long in that duty.
- The pin is soft, worn or scored. Aluminum bronze will cut it. Use a leaded tin bronze, or replace the pin.
- Sustained temperature above about 300 °C (572 °F). Look at steel-backed graphite or a purpose-designed high-temperature alloy; check the housing and shaft limits at the same time.
- Alignment cannot be held. Where the structure flexes, a leaded bronze tolerates edge loading better than a hard, high-strength alloy.
Excavator linkage is the most common replacement request we handle; the excavator bushing and wrapped bronze bushings used in crane service pages show the forms usually drawn for those two machine families.
What to send for a quotation. Drawing or dimensions (ID, OD, length, any flange or collar), operating load and oscillation angle or speed, temperature range, pin material and hardness, whether grease reaches the joint, medium and contamination level, and monthly quantity.
Frequently Asked Questions (FAQs)
Send the joint conditions, not just the part number
Give us the load, oscillation angle, temperature range, pin material and whether grease reaches the joint, plus the drawing or sample dimensions. We will confirm which alloy fits, flag anything in the design that shortens service life, and quote against the drawing.
