Solid-Lubricant Bronze Bushings for Mining Equipment
Solid-Lubricant Bronze Bushings for Mining Equipment
High-Performance Self-Lubricating Bronze Bushing Solutions & Technologies. Minimize downtime, extend service life, and reduce costs for dynamic applications.
Solid-Lubricant Bronze Bushings for Mining Equipment
A solid-lubricant bronze bushing, also sold under trade designations such as JDB and JFB, is a plain bearing in which graphite or a comparable solid lubricant is embedded in a cast bronze base. In mining service it is a narrow-fit answer with real advantages, and it is routinely specified into positions where it is the wrong answer. This guide sets out where the material belongs, what the published limits are, where the sources disagree, and what has to be confirmed before an order is placed.
1How the material works
A solid-lubricant bushing is a three-layer construction, and the division of labour between the three layers is what determines whether the material is fit for a position.
| Layer | Function | Typical published requirement |
|---|---|---|
| Steel housing bore | Carries and locates the bush | H7 housing bore |
| Cast bronze base with embedded solid lubricant | Carries the specific pressure and the PV product. Graphite area fraction is commonly designed in the 20 to 35 percent band | Graphite plugs, grooves or bars pressed into the base under interference |
| Steel pin or journal | Does not carry the load. Its function is to provide a hard enough, smooth enough counterface for the transfer film to form and hold | Journal hardness 40 to 45 HRC or above, surface roughness Ra 0.8 micrometre or better |
The self-lubricating action is a transfer film, not a reservoir. Friction heat and shear at the interface push graphite particles out of the base and onto the journal surface, where they build a film that changes the contact from metal against metal into film against metal. That film is the lubrication mechanism, and it is also the failure point: if the journal is too soft or too rough, the film is ploughed out repeatedly, friction and temperature rise, the graphite inserts are consumed, and the base deforms plastically.
Two conditions that are not optional
Running-in is part of the installation. Before the bush carries load, apply a small quantity of high-temperature grease and run the joint unloaded at low speed for 2 to 4 hours so the transfer film forms evenly. A joint that is loaded before the film exists does not form a film, it scrapes the journal unevenly. This step is the single most common cause of early failure in this product class, and it belongs in the commissioning instructions rather than in the maintenance manual.
Two failure modes cannot be diagnosed after assembly. Cracking in the plug bore, and the hidden fracture line at the press-fit interface, are not visible or measurable once the bush is in the housing. They appear as an occasional early failure rather than as progressive wear, which is why these positions are often better managed on a planned replacement interval than on a breakdown response.
Because the transfer film needs a hard counterface and a low sliding speed to hold, this material class is inherently a slow-motion material. That single fact drives most of the selection decisions in section 6.
2What the designation tells you, and what it does not
Designation systems for this product class are used loosely, and an order that carries only a trade prefix is not a specification. Three layers of information are involved, and they answer different questions.
| Layer | Identifier | What it is authoritative for | Basis |
|---|---|---|---|
| National standard | GB/T 23894-2009 Plain bearings — Copper alloy bearings with embedded solid lubricant |
Material system and performance requirements. A cast copper alloy complying with GB/T 1176 is the base; solid lubricant such as graphite, PTFE or molybdenum disulphide is embedded in holes in the base. The standard defines four structure types and does not define a JDB or JFB type designation | Standard |
| Structure type | Straight sleeve, flanged sleeve, thrust washer, slide plate | Geometry. Some manufacturer catalogues write the same four types as WQZ, WQZD and WQP. JDB generally corresponds to the straight sleeve and JFB generally corresponds to the flanged sleeve | Standard |
| Trade and manufacturer designation | JDB-1, JDB-2, JDB-3, JDB-4, JDB-5, JFB | Nothing. The numeric suffix identifies the base material, not a performance grade, and the prefix does not identify a copper base. JDB-3 denotes a steel bush, JDB-4 cast iron, JDB-5 bearing steel | Manufacturer catalogues |
Three designations that are not the basis for a mining order
JB/T 3729-2008, Oily bronze graphite bearing. This is maintained by the electrical carbon standards committee, with an ICS classification in the electrical carbon products group. Its scope is small and miniature electric motors, of the type used in vehicles, washing machines and fans. The size and load scale is not comparable with heavy mining duty, and this document is not a source for a mining specification.
JB/T 2560 to 2563-2007, Plain bearing housings. These cover the types and dimensions of plain bearing housings, not the bush itself. They are frequently cited as though they were a bearing specification.
GB/T 23894-2009 does not replace an earlier bearing standard. It is a first issue. JB/T 6987 is a software standard for manufacturing resource planning system prototyping and is unrelated to bearings.
For an order, the specification needs five elements rather than a trade prefix: the standard, the structure type, the base alloy with its UNS number, the dimensions, and the lubrication and fit requirements.
| Base alloy system | Chinese grade | UNS | EN | Composition, weight percent | Orientation for this product class |
|---|---|---|---|---|---|
| High-strength brass | ZCuZn25Al6Fe3Mn3 | C86300 | CC762S | Cu 60–66 / Zn 22–28 / Al 5–7.5 / Fe 2–4 / Mn 2.5–5 / Sn 0.2 max | Higher load capacity and higher PV than the tin bronze base. The harder base gives up some ability to embed abrasive particles, so the journal is more exposed |
| Tin bronze | ZCuSn10P1 | C90100 | CC483K | Sn 9.0–11.5 / P 0.5–1.0 / Pb 0.3 max | Soft base embeds hard particles and protects the journal. Lower PV and speed limits than the brass base. The usual first choice where the medium carries grit |
| Lead-bearing tin bronze | ZCuSn5Pb5Zn5 | C83600 | CC491K | Sn 4–6 / Pb 4–6 / Zn 4–6 | Easy to machine, good oil retention. Lead content is restricted in some destination markets, so check the target market and the customer specification |
| Aluminium bronze | ZCuAl10Fe3 | C95200 | CW307G | Al 8.5–11.0 / Fe 1.0–4.0 / Sn 0.3 max / Pb 0.2 max | Corrosion and creep resistance, the metal option for acidic mine water. High hardness reduces particle embedding and raises the risk of scoring the journal |
| Nickel aluminium bronze | ZCuAl9Fe4Ni4Mn2 | C95800 | CB333G | Al 8.5–10 / Fe 4–5 / Ni 4–5 / Mn 0.8–2.5 | High strength with corrosion resistance, an option where slurry or seawater is present |
| Grey cast iron | HT250 | — | — | C 3.0–3.5 / Si 1.5–2.5 | Lowest cost with a high temperature ceiling. Hard for a graphite insert, so the PV limit is low |
Two published divergences that affect the order
The UNS number for CuAl10Fe3. Copper alloy database listings give C95200 for CuAl10Fe3, while a great deal of catalogue literature writes C95400 for the same alloy name. The two designations carry different iron ranges. State the specific UNS number on the order rather than the alloy name alone.
Four ways of writing the high-strength brass grade. ZCuZn25Al6Fe3Mn3, ZCuZn25Al6Fe3Mn4, ZCuZn24Al6Fe3Mn3 and ZCuZn25Al5Mn4Fe3 all appear in catalogues. The difference between the Mn3 and Mn4 suffixes is not explained in any published standard. Write the grade as GB/T 1176 gives it and name the source of the material.
3Published material data, with source basis
The figures in this section are typical values published in bearing industry technical documentation for a cast tin bronze base with embedded solid lubricant, in two published grades. The source states the values as typical and not as standard values, and states that the base metal contains lead.
How to read the basis column
Standard means the figure is a requirement of the cited standard. Typical means it is a manufacturer-published indicative value, not a minimum. Derived means it is calculated here from other published figures, and the calculation is shown. A typical value is a starting point for screening, not a limit to be designed against without a test report.
| Property | Grade 1 | Grade 2 | Note | Basis |
|---|---|---|---|---|
| Density, g/cm³ | 8.8 | 8.7 | Typical | |
| Tensile strength, N/mm² | 195 | 245 | Typical | |
| Elongation, percent | 15 | 15 | Typical | |
| Compressive strength at 0.2 percent, N/mm² | 95 | 130 | Typical | |
| Impact strength, J/cm² | 10 | — | Not published for Grade 2 | Typical |
| Hardness HBW | 60 | 70 | Typical | |
| Longitudinal elastic modulus, N/mm² | 83 000 | 103 000 | Typical | |
| Coefficient of linear expansion, 10⁻⁵ per °C | 1.8 | 2.0 | Typical | |
| Thermal conductivity, W/(m·K) | 71.1 | 75.3 | Typical | |
| PV limit, dry friction, N/mm²·m/s | 1.00 | 1.00 | The governing limit for an unlubricated joint | Typical |
| PV limit, periodic lubrication, N/mm²·m/s | 1.65 | 1.65 | Applies where lubricant is applied on a schedule | Typical |
| Maximum sliding speed, dry friction, m/s | 0.40 | 0.40 | Independent of the PV limit. See section 4 | Typical |
| Maximum sliding speed, periodic lubrication, m/s | 0.85 | 0.85 | Typical | |
| Maximum specific pressure, N/mm² | 15 | 15 | Applies to static or incipient motion at 0.0017 m/s and below. Not a running-load rating | Typical |
| Working temperature range, °C | −40 to +250 | −40 to +250 | Reduced to +250 °C upper limit under periodic lubrication, per the source | Typical |
| Sliding surface roughness, micrometre | Rz 6.3–12.5 | Rz 6.3–12.5 | On the bush | Typical |
| Counterface material used in the published test | S45C | S45C | Test condition, not a recommendation | Typical |
| Machining tolerance grade, JIS | ID 7–8 / OD 6–7 / L 8–9 | Same | Typical |
Basis note for Table 3.1
Not guaranteed minimum values for any individual part. The source states that the base metal contains lead, so where the destination market applies a lead restriction, the lead content of the specific grade has to be checked against the order. The values that apply to a part number supplied by VIIPLUS are those in the test report and inspection document issued with that order.
One figure in this table is disputed. The 15 N/mm² maximum specific pressure is a static or incipient motion value. Other material data for solid-lubricant inserts in general states 100 to 120 N/mm² static and 70 to 90 N/mm² dynamic. These are not the same claim, and the gap has not been reconciled in any single published source. This page uses 15 N/mm² with its motion condition attached, and treats the higher figures as a figure to be confirmed against the test report for the specific part. Where a static load calculation is the basis of a decision, that test report is the document to request.
| Property | High-strength brass base, no lubricant | High-strength brass base, oil lubricated | Basis |
|---|---|---|---|
| Permissible PV, N/mm²·m/s | 1.65 | 3.25 | Typical |
| Permissible sliding speed, m/s | 0.5 | 1.0 | Typical |
| Permissible specific pressure, N/mm² | 28 | 15 | Typical |
| Hardness HB | 220 | — | Typical |
| Temperature range, °C | −40 to +300 | −40 to +150 | Typical |
| Coefficient of friction | 0.03 to 0.20 | — | Typical, oscillating test |
Basis, and two points on this table
The source for each row is the same body of published documentation used for Table 3.1.
There is no single PV value for this material class. The published dry friction PV limit is 1.00 N/mm²·m/s for the tin bronze base and 1.65 N/mm²·m/s for the high-strength brass base. A general figure quoted as the PV limit for solid-lubricant bushings, without naming the base alloy and the lubrication state, is not a usable specification. Use the value for the alloy and the duty you are actually specifying.
A published divergence on oil-lubricated sliding speed. One source states 1.0 m/s for the oil-lubricated high-strength brass base, and another states up to 5 m/s for the same duty. The second is not consistent with the published PV limit for that base, since 1.65 divided by 5 gives 0.33 N/mm², well below any running load. The lower figure is used here.
Temperature note
Two temperature ceilings appear in the published material for the same product class: +250 °C for the tin bronze base in Table 3.1, and +300 °C for the high-strength brass base in Table 3.2, with the oil-lubricated condition reduced to +150 °C. These are per base alloy and per lubrication state rather than a single figure for the product class. Where the duty approaches the ceiling, request the material data and the test report for the specific alloy and lubrication condition rather than relying on a value taken from a general table.
4The pressure, speed and PV relationship
This is the most common selection error in this product class, and it is worth stating precisely because the published limits look like they can simply be multiplied.
The maximum pressure and the maximum speed cannot be used together
For the tin bronze base, the published maximum specific pressure is 15 N/mm² and the published maximum dry sliding speed is 0.40 m/s. Taking both at once gives 15 multiplied by 0.40, which is 6.0 N/mm²·m/s. The published PV limit for the same base is 1.00 N/mm²·m/s, so that combination is six times the limit. The two figures are independent limit values, and the constraint that governs is the PV product.
On the PV curve for this base: at 15 N/mm² the permitted sliding speed is 0.067 m/s. At 0.40 m/s the permitted specific pressure is 2.5 N/mm². Any check that multiplies the two published maximum values, or that uses the 15 N/mm² figure as a running-load rating, arrives at a result the material cannot sustain.
Every load and speed decision for this material class therefore has to be made on the PV curve. The formula is straightforward, and the only part that goes wrong in practice is the unit conversion of the diameter.
v in m/s, n in r/min, d in metres, p in N/mm², PV in N/mm²·m/s
The diameter unit is where the arithmetic goes wrong
The bore diameter has to be substituted in metres. A 240 mm bore is 0.24 m. If the diameter is entered in millimetres while the formula expects metres, every result is out by a factor of a thousand.
Worked check: a 240 mm bore at 40 N/mm² gives a permitted speed of 1.00 divided by 40, which is 0.025 m/s, and a rotational speed of 60 multiplied by 0.025 divided by π multiplied by 0.24, which is 2.0 r/min. This is the entry for that size in Table 5.1, and the whole table was computed with an independent script.
Which limit binds first
There are three limits, and which one binds depends on the position. This is the reason a single number cannot be quoted for the material class.
| Duty condition | Limit that binds | Practical consequence |
|---|---|---|
| Heavy load, very low speed, oscillating | PV limit, at a specific pressure above the static rating | The material is at its most suitable. Load is high, motion is slow, and the transfer film has time to establish |
| Light load, higher speed | Maximum sliding speed | Beyond 0.40 m/s dry on the tin bronze base, the film cannot be sustained regardless of load |
| Heavy load, continuous rotation | Both, and the speed limit binds first | At continuous running speed the sliding speed limit is reached long before the PV limit, so the material is excluded on speed rather than on load |
| Static or barely moving joint | Maximum specific pressure | At 0.0017 m/s and below the published 15 N/mm² applies, and the PV limit is not close to being reached |
5Screening speed and load by bore diameter
Where a specific size has not been fixed yet, the table below gives the rotational speed at which each bore diameter reaches the PV limit, for a range of specific pressures. It answers one question: is the speed of this position physically possible for this material.
| Bore diameter, mm | Specific pressure p, N/mm² | |||
|---|---|---|---|---|
| 5 | 10 | 20 | 40 | |
| 50 | 76.4 | 38.2 | 19.1 | 9.5 |
| 80 | 47.7 | 23.9 | 11.9 | 6.0 |
| 120 | 31.8 | 15.9 | 8.0 | 4.0 |
| 160 | 23.9 | 11.9 | 6.0 | 3.0 |
| 200 | 19.1 | 9.5 | 4.8 | 2.4 |
| 240 | 15.9 | 8.0 | 4.0 | 2.0 |
| 300 | 12.7 | 6.4 | 3.2 | 1.6 |
Basis and how to read Table 5.1
Derived. Computed from the published dry friction PV limit of 1.00 N/mm²·m/s for a tin bronze base, using the relationship v = PV ÷ p and n = 60v ÷ (πd). The table is therefore computed at the published limit for the most common base alloy, and not at an adjusted, averaged or rounded value. If the base alloy is a high-strength brass base with a published dry PV limit of 1.65 N/mm²·m/s, the admissible speeds are higher by a factor of 1.65, and Table 7.2 gives the scaling factor for each material family. Where a test report for the specific part states a different limit, that limit governs and this table is a screening reference only.
Read the table as follows. The larger the bore, the lower the admissible speed. A large-diameter part can only be an oscillating joint; it cannot be a continuously rotating part. If a position with a bore above 200 mm is specified at a running speed of more than a few tens of r/min, the duty is outside what this material can do, and the position has to be recalculated as a thick-walled cast aluminium bronze bush, a steel-backed bimetal bearing, or a rolling bearing.
| Bore, mm | Working length, mm | Specific pressure, N/mm² | Allowable radial load, kg | Basis |
|---|---|---|---|---|
| 50 | 50 | 15 | 37 | Derived |
| 120 | 120 | 20 | 288 | Derived |
| 240 | 240 | 10 | 576 | Derived |
Basis note for Table 5.2
Derived from the published specific pressure values, with the working length set equal to the bore diameter for the three examples shown. Radial load, W = d × L × p / 1000 in kg, with d and L in mm and p in N/mm². The formula scales linearly with length, so a different working length is a direct multiple of these figures. The load is the radial component carried by the bush; the effect of an axial force, an inclination moment, or an uneven load distribution across the length is not included in this calculation and has to be checked separately.
6Where these bushings fit in mining equipment
The tables in this section are the core of the guide. The applicability column is deliberately uneven, because for a large number of mining positions the answer is that this material is not the right one, and a guide that implied otherwise would be less useful than a guide that did not exist.
Two evidence levels are used. Documented means the position has a public source, such as a spare parts list, a procurement document, a patent or an equipment technical page. Common practice means the position is included on general engineering practice, without a public primary source.
Positions where solid-lubricant bushings are a candidate
| Equipment and position | Motion | Load | Medium | Applicability | Controlling condition and notes | Evidence |
|---|---|---|---|---|---|---|
| Open pit | ||||||
| Drill rod centraliser and rod guide, top-hammer and down-the-hole rigs | Oscillating and linear | Light | Slurry, dust | Candidate | Low speed, very low PV, and no lubricant available. The part guides and steadies the rod and prevents the rod from swinging off axis | Documented |
| Rod handler and rod changer pivot, top-hammer rigs | Pivoting | Light to medium | Slurry, oil film | Candidate | The handler is built from an upper and a lower body with a clamping cylinder, so the pivot carries a light load | Documented |
| Hoist pivot and hoist cylinder eye, mining trucks | Pivoting | Impact, heavy | Dust, slurry | Conditional | Self-lubricating bronze bushes appear in spare parts configurations for this position. Where the duty is shock dominated, a hardened steel pin with an oil way is a parallel option | Common practice |
| Underground | ||||||
| Drill mount cradle and anti-vibration cradle, roadheaders and drill jumbos | Pivoting | Medium, frequent oscillation | Coal slurry, dust | Candidate | A high-frequency oscillating joint where relubrication is difficult to arrange. The impact spectrum has to be checked; a static load calculation is not sufficient | Common practice |
| Boom feed swivel and feed beam support, roadheaders and drill jumbos | Reciprocating, oscillating | Medium | Coal slurry, water | Candidate | Low speed with a moderate PV | Common practice |
| Drill boom pivot, bolter jumbos and drill rigs | Pivoting | Medium | Dust, water ingress | Candidate | Light to medium load with frequent oscillation | Common practice |
| Drilling and auxiliary | ||||||
| Reel centre shaft, cable and water hose reels | Continuous rotation | Light to medium | Dust, rain and snow | Candidate | Relubrication is the constraint rather than the load. The position is often high up or in a restricted rotating space. A flanged type is used where axial location is needed | Common practice |
| General pivot eyes, link pin bores, hinged brackets | Pivoting | Light to medium | Dust, humidity | Core application | The main body of use for this material: no lubricant required, particle embedding, journal protection, and a low cost at low PV. Limited to oscillating and low-speed duty, and it does not replace a heavy shock position | Common practice |
Positions where a different material is normally used
For the positions below, published spare parts documentation and equipment technical pages point to a different material family. The reasons are given so that a substitution can be judged rather than assumed.
| Equipment and position | Motion and load | Medium | Applicability | Material normally used, and the reason | Evidence |
|---|---|---|---|---|---|
| Mineral processing and crushing | |||||
| Ball mill and rod mill trunnion liner | Continuous rotation, impact heavy | Slurry with abrasive grit | Not suitable | Carbon steel or white iron. Published wear part documentation specifies these, with a service life commonly stated at 12 to 18 months. The abrasive slurry condition is the deciding factor, not the load | Documented |
| Ball mill main trunnion bearing | Continuous rotation, high static load | Circulating oil, slurry | Not suitable | Babbitt, or a split double-row spherical roller bearing. With an oil circulation and cooling system already present, a solid lubricant adds nothing | Documented |
| Cone crusher eccentric bushing liner | Continuous rotation with oscillation, impact heavy | Dust, oil mist | Not suitable | High lead bronze liner, screw fixed. This position does use a plain bearing with a copper alloy, but the material is a cast high lead bronze or aluminium bronze, not a solid-lubricant insert | Documented |
| Cone crusher frame bushing and spherical washer | Oscillating, high static load | Dust | Not suitable | High lead bronze with aluminium bronze thrust faces. A published patent identifies replacement of the traditional bronze bush with a rolling bearing as the improvement direction | Documented |
| Flotation agitator shaft sleeve and packing seal | Continuous rotation, 200 to 400 r/min | Acidic slurry with solids | Not suitable | A double bearing with a mechanical or packing seal, and a wear sleeve in high strength steel with a coating. At 200 to 400 r/min a small bore is already beyond the sliding speed limit, and acidic media attacks the graphite | Common practice |
| Slurry valve trim | Sliding open and close, high static load | Strongly erosive slurry | Not suitable | Cast basalt or hard alloy lining. Erosion and edge chipping | Documented |
| Flotation and thickener impeller, rake centre shaft | Continuous rotation, impact and high static load | Strongly erosive slurry | Not suitable | Moulded wear rubber or polyurethane. Tearing and washout | Documented |
| Conveying | |||||
| Belt conveyor idler shaft | Continuous rotation, light but high frequency | Dust | Not suitable | Deep groove ball bearing from the standard size series. A standard part is available in both lead time and cost | Documented |
| Conveyor head, tail and bend pulley shaft | Continuous rotation, heavy | Dust, humidity | Not suitable | Spherical roller bearing with a bearing housing assembly | Documented |
| Bucket elevator head and tail shaft | Continuous rotation, heavy | Dust, bulk material | Not suitable | Spherical roller bearing. Procurement technical documents specify a spherical roller bearing for the main shaft | Documented |
| Scraper conveyor sprocket shaft | Continuous rotation, heavy | Coal slurry | Not suitable | Spherical roller bearing, reinforced series | Documented |
| Conveyor chute and cleaner | Linear reciprocating | Abrasive flush | Not suitable | Wear resistant steel, high chromium cast iron or polyurethane | Common practice |
| Open pit and mobile equipment | |||||
| Boom and stick pin bush, electric shovel and hydraulic excavator | Pivoting, medium with shock | Dust, mud | Not first choice | Oil-lubricated hardened steel bush, steel-backed bimetal, or a metal-polymer composite. Published technical material states that oil-lubricated types account for about 90 percent, and that maintenance-free bushes have weaker impact resistance and do not hold up under long heavy-duty digging | Documented |
| Arm and bucket pin bush, electric shovel | Pivoting, medium | Dust, slurry | Not first choice | Steel-backed sintered bronze with a PTFE layer. Modern replacement parts for this class of equipment are predominantly composite types | Documented |
| Tooth adapter bushing, bucket teeth | Reciprocating with shock | Dust, abrasive grit | Not suitable | Cast steel or high manganese steel as a solid wear part. Impact resistance and abrasion resistance are both insufficient in this material | Common practice |
| Dump chute and chute liner | Linear reciprocating | Abrasive flush | Not suitable | Wear plate, high chromium cast iron or polyurethane. A copper base is not abrasion resistant and thins under erosion | Common practice |
| Track roller and idler shaft, shovel and bulldozer | Continuous rotation, impact heavy | Slurry, mud | Not suitable | Tapered roller or spherical roller bearing. Continuous rotation with shock | Common practice |
| Slew bearing | Continuous rotation, high static load and overturning moment | Dust, mud | Not suitable | Ball or three-row cylindrical slewing bearing. A rolling element construction | Documented |
| Axle knuckle and steering joint, mining truck | Continuous rotation, medium | Slurry, sand dust | Not suitable | Tapered or spherical roller bearing with the steering king pin, grease lubricated | Common practice |
| Underground | |||||
| Coal machine cutter section | Continuous rotation, impact heavy | Coal dust, coal slurry | Not suitable | Full complement cylindrical roller bearing | Documented |
| Coal machine rocker arm pivot | Pivoting, impact heavy | Coal slurry | Not suitable | Rolling bearing, per the spare parts catalogue | Documented |
| Coal machine traction and travel section | Continuous rotation, heavy with frequent reversal | Coal slurry, severe humidity | Not suitable | Double row tapered roller or spherical roller bearing. Published failure lists for this duty record spalling, dust wear, water ingress corrosion and seal failure | Documented |
| Roof support jack pivot, hydraulic support | Reciprocating, medium with high static load | Coal slurry | No public source | Spare parts catalogues generally do not separate the bush, and the position is often a solid 40Cr hardened pin | Common practice |
| Other equipment | |||||
| Vibrating screen exciter bearing | High frequency rotation, 750 to 1400 r/min with strong vibration, impact heavy | Dust, humidity | Not suitable | Special large clearance cylindrical, spherical or self-aligning roller bearing, grease lubricated with a labyrinth or light oil circulation. Intermittent lubrication and the wear rate at this frequency are not acceptable in a plain bearing | Documented |
| Rotary head spindle, top-hammer and down-the-hole rigs | Continuous rotation, medium with shock | Slurry, dust | Not suitable | Cylindrical or tapered roller bearing, as identified in published patent material | Documented |
| Rotary table bearing, drill rig | Slow rotation, high static load with overturning | Slurry | Not suitable | Double row cylindrical roller bearing | Common practice |
| Slurry and sand pump sleeve and wear plate | Continuous rotation, heavy abrasive flush | Sandy slurry | Not suitable | High chromium cast iron Cr26 or Cr27, 3Cr13 or 4Cr13, stainless steel, rubber lining, polyurethane, ceramic or tungsten carbide, or high manganese steel. A copper base is not among the listed options | Documented |
| Gearbox and reducer bushing | Continuous rotation, medium | Oil mist | Not first choice | Rolling bearing or a Babbitt bearing. The oil film is already present | Common practice |
| Classification and cyclone sleeve | Continuous rotation, light to medium | Slurry, wet | Not first choice | Rolling bearing with a stainless steel or high chromium sleeve. A copper base does not have sufficient slurry corrosion resistance | Common practice |
The boundary in one sentence
A solid-lubricant-insert bushing is the right material where three conditions hold at the same time: the motion is low-speed reciprocating or oscillating, the position cannot be relubricated or it is impractical to do so, and the medium carries abrasive particles while the counterface must not be scored. Remove any one of those three conditions and the advantage over a wrapped bronze bush disappears, because a wrapped bush with an oil reservoir is the better answer for a position that can be greased.
7Duty class and media against material
| Material family | Impact led | Extreme pressure, low speed | Continuous rotation | Abrasive contamination | Low speed, oscillating, no relubrication |
|---|---|---|---|---|---|
| Solid lubricant, tin bronze base | No | Check | No | Yes | Yes |
| Solid lubricant, high-strength brass base | No | Yes | No | Check | Yes |
| Solid lubricant, aluminium bronze base | No | Yes | No | No | Check |
| Wrapped bronze bush | Check | Yes | Yes | Check | Check |
| Cast tin bronze | Check | Yes | Yes | Yes | Check |
| Cast aluminium bronze | Yes | Yes | Yes | No | Check |
| Steel-backed bimetal | Yes | Yes | Yes | Check | Check |
| Oil-impregnated sintered bush | No | No | Check | No | Check |
| Engineering plastic bush | No | No | Check | Check | Yes |
| Rolling bearing | Yes | Yes | Yes | Check | No |
How to read Table 7.1
Yes means the family is normally the first consideration for that duty class. Check means it can be used with additional verification of the stated conditions. No means the family is normally not used there, and for most of the No entries the reason is mechanical rather than commercial. For the explosive path duty class, every metal family in this table is excluded, and that is set out separately in section 11 rather than repeated here.
| Material family and lubrication state | PV limit, N/mm²·m/s | Scaling coefficient | Speed at bore 120 mm and 10 N/mm², r/min | Lubrication requirement | Basis |
|---|---|---|---|---|---|
| Solid lubricant, tin bronze base, dry | 1.00 | × 1.00 | 15.9 | No periodic lubrication, subject to a 2 to 4 hour running-in | Typical |
| Solid lubricant, high-strength brass base, dry | 1.65 | × 1.65 | 26.3 | No periodic lubrication | Typical |
| Solid lubricant, aluminium bronze base | 2.20 | × 2.20 | 35.0 | No periodic lubrication | Typical |
| Wrapped bronze bush, grease lubricated | 2.80 | × 2.80 | 44.6 | Relubrication required on a schedule | Typical |
| Cast aluminium bronze | 3.50 | × 3.50 | 55.7 | Relubrication required on a schedule | Typical |
| High lead tin bronze | 5.01 | × 5.01 | 79.7 | Relubrication required on a schedule | Typical |
Two published values that are frequently quoted incorrectly
A PV value of 3.6 N/mm²·m/s for POM is not a plastic bush value. It belongs to a three-layer composite of steel backing, sintered bronze and a polymer bearing surface. A solid engineering plastic bush has a dry friction PV in the region of 0.1 to 0.3 N/mm²·m/s, which is an order of magnitude lower, and the confusion between the two is a frequent source of error in selection documents.
For an oil impregnated sintered bush, use 0.8 to 1.8 N/mm²·m/s as a design value, with 1 to 3 as the extreme. Once the pores are blocked, the friction coefficient rises from 0.05 to 0.15 into the region of 0.2 to 0.3.
Basis and limits of Table 7.2
Every PV limit in this table is a typical published value, and not an assured minimum for an individual part. The scaling coefficient is that published limit divided by the 1.00 N/mm²·m/s dry friction limit published for a tin bronze base, and the speed column is the same limit applied at a bore of 120 mm and a specific pressure of 10 N/mm².
Published PV figures for cast aluminium bronze differ between sources. The value used in this table is 3.50. Other published sources give 1.25 for dry friction and 4.38 for an oil-lubricated condition at 31 N/mm² and 1.14 m/s. For open pit dry duty the lower figure applies.
This table compares order of magnitude within one PV framework. It is not a licence to substitute one scheme’s allowable value for another’s, because the lubrication states differ in kind. A dry friction PV and a grease lubricated PV cannot be used interchangeably, and the failure mechanisms differ as well: a fatigue crack in a casting, a seam opening in a wrapped bush, and a blocked pore in a sintered bush are three different events. Changing material means changing the lubrication method and the fit requirements at the same time, and re-running the failure mode check.
Because the values come from different published sources with different test methods, the comparison is an order of magnitude screening aid and not a like-for-like test result. Where a decision is close to a limit, the value to use is the one from the test report for the specific part, and the lower figure where two sources disagree.
8A five-step selection sequence
| Step | Question to answer first | Decision point | Outcome |
|---|---|---|---|
| 1 | Is the motion continuous rotation, reciprocating, or pivoting oscillation? What is the working speed in r/min and the sliding speed in m/s, and the frequency? | Continuous rotation excludes the material on the sliding speed limit, which is 0.40 m/s dry on the tin bronze base. Check the speed before the load | If continuous rotation, go to a rolling bearing or a cast bronze bush with a designed oil film. If reciprocating or oscillating, continue |
| 2 | Does the medium carry abrasive particles such as quartz or silica dust? Does it contact acidic mine water, and at what pH? What is the continuous working temperature? | Direct contact with acidic mine water excludes this material and the copper base alloys. Above the temperature ceiling for the alloy, the material changes | For acidic contact, move to cast aluminium bronze and run a mine water coupon test first, or to an engineering plastic. Above the ceiling, move to a different material |
| 3 | Can the position be greased? How long does a shutdown take for access? Is the position high up, suspended, in a confined housing, or in a restricted rotating space? | This is where the material earns its place. If relubrication is possible, the advantage over a wrapped bush is not established | Not greasable, continue and the case for this material is established. Greasable, a wrapped bronze bush is generally the better answer |
| 4 | What is the measured journal hardness and the surface roughness Ra? Can the journal be brought to 45 HRC and above with Ra 0.4 micrometre? | At 45 HRC with abrasive particles in the medium, the transfer film is repeatedly ploughed out and the life scatter increases by an order of magnitude | Do not specify this material until the journal is corrected. Where it cannot be corrected, the material is not suitable for that position |
| 5 | Is the bore above 150 mm? Is axial location needed? Is a split installation needed? | Above 150 mm the process for embedding the inserts becomes impractical, and the material has to be changed | Above 150 mm, move to a split bearing with replaceable graphite blocks, or to a steel-backed bimetal bearing, or to a cast aluminium bronze bush. For axial location, a flanged type. For a split installation, a split housing |
The safety filter runs after the technical questions, not instead of them
If the position contacts ammonium nitrate or a nitrate based explosive, every copper based material is excluded, including this product class, wrapped bronze, tin bronze, aluminium bronze and steel-backed copper liners. The exclusion is a safety requirement and it is not decided on load capacity. Section 11 sets out the basis.
Why the process becomes impractical above 150 mm
There is no published standard tolerance for this limit, so the following is engineering derivation, and the constraint is real in manufacturing terms rather than in the standard.
- The inserts scale with the load area. As the bore grows, the plug bore grows with it, and a single plug eventually exceeds what graphite can carry in compression and resist in brittle fracture. The tensile and flexural strength of graphite does not rise with the base alloy, and the stress concentration at the plug bore edge increases with the diameter to length ratio. The 20 to 35 percent area fraction that works at small diameters has to rise at large diameters, which thins the load carrying section further.
- Groove end stress concentration. At a length to diameter ratio of two, the circumferential stiffness of the base drops and the pressed graphite bar is prone to lifting out of its groove.
- Press fit eccentricity becomes uncontrolled. A 300 mm bore needs a machined bore and a controlled press fit or a thermal fit. A wall thickness difference of 0.1 mm is enough to load the inserts unevenly.
- The heat path lengthens. Graphite conducts at roughly 50 to 100 W/(m·K) and heat travels along the insert through the base, so at large diameters friction heat accumulates at the edge and accelerates insert oxidation.
The practical routes above 150 mm are a split bearing with replaceable graphite blocks, so a single block stays within a manufacturable size and can be replaced instead of scrapping the whole bush; a steel-backed bimetal bearing, which carries the static load in a thin wall at large size; a solid cast aluminium bronze bush with centralised lubrication; or a rolling bearing, where life is calculable to ISO 281 and condition can be monitored by vibration.
9Counterface, fit and running-in requirements
| Item | Requirement | Note on the basis |
|---|---|---|
| Journal hardness | 40 to 45 HRC or above | Manufacturer requirement. No published national standard states this figure for this product class |
| Journal surface roughness | Ra 0.8 micrometre or better | Manufacturer value. A surface that is too smooth does not hold the film either |
| Bush sliding surface roughness | Rz 6.3 to 12.5 micrometre | Manufacturer value |
| Housing bore fit | H7 | Manufacturer value |
| Clearance between bore and journal | 0.15 to 0.55 mm, depending on the journal diameter | Manufacturer value |
| Journal and bore fit combination | Not stated | No primary source was found for an H7 and k6 combination for this product class. Tolerance bands on the bore side differ between manufacturers, so this is not written onto a drawing as a standard value |
| Running-in | Small quantity of high temperature grease, then 2 to 4 hours unloaded at low speed | Required to establish the transfer film. This step establishes whether the joint works |
| Counterface for other product families | Journal hardness 150 HB and Ra 1.6 micrometre or better | This is the general rule for our other product families. It does not apply to the solid-lubricant-insert family covered on this page, which has the more demanding 40 to 45 HRC and Ra 0.8 micrometre requirement. The requirement for the specific family has to be stated on the order |
The counterface is part of the bearing specification, not part of the customer’s general notes
When the journal is at 45 HRC with a surface roughness of 0.8 micrometre, the transfer film is repeatedly ploughed out by hard particles, and the life scatter increases by an order of magnitude. The journal hardness and roughness are therefore a condition of the material working, and they belong in the technical conditions of the order and the drawing, not in a general note that the customer maintains the shaft.
10Replacement criteria and maintenance
When the bush is due for replacement
Any one of the following four indications means the part is replaced. There is no case for running it further and reassessing.
- Measured bore increase has reached three times the initial clearance.
- Base metal is visible on the sliding surface.
- Local temperature rise is abnormal for the position.
- The transfer film has disappeared and the friction coefficient has risen with it.
Planned replacement rather than breakdown replacement
Cracking in the plug bore and the hidden fracture at the press fit cannot be diagnosed in service, and they present as an occasional early failure rather than as progressive wear. For positions where a stoppage is expensive, managing the position on a planned replacement interval is the more practical approach. The interval has to be set from the duty and the failure history, and it is a management decision on the expected life rather than on the worst case.
Housing bore repair
Where a housing bore is worn and has to be restored, a liner in a steel-backed bimetal bearing is generally more practical than a one-off custom part, because it moves the repair from a fully custom size to a standard part plus a machining operation on the housing. Where the housing itself is the damaged item, that operation still has to be assessed separately.
Storage and handling
The pressed graphite insert structure is brittle. Drop and impact during transport and storage can create a crack in the plug bore, so packing and handling have to prevent falls. A visual inspection of the bore on receipt is a practical check, since this is the one defect that can be seen before assembly.
11Explosive path material restriction
No copper alloy in the ammonium nitrate path
Copper and copper alloys are excluded from equipment that contacts ammonium nitrate. Contact between copper and ammonium nitrate can produce tetraamminecopper nitrate, a compound that is sensitive to impact, with an equivalent initiation energy comparable to a 2 kg weight dropped from 20 cm. Any impact or hot work on such a part can initiate a local explosion.
Regulatory guidance requires that mixing and packaging equipment be made of materials that do not generate sparks and are compatible with the ammonium nitrate components, that bearings and drive components be located outside the mixer, and that ammonium nitrate dust accumulation be prevented. Zinc, copper, lead and galvanised iron are called out as materials not to use.
The consequence for a bearing order is specific. The auger, metering pump, sealing elements and hose guide wheels on a blasting or mixing vehicle are built in stainless steel, cast iron, polyacetal, PTFE or aluminium, with physical separation from the explosive path. This is a safety requirement, and load capacity is not a basis for releasing a copper part into that service. Where a copper part is already installed, it should be treated as a suspect item, checked against the applicable safety notice, and no impact or hot work applied to it.
12Source basis and open questions
The figures on this page come from national standard information systems, industry ministry standard announcements, a copper alloy database, published manufacturer technical documentation, mine safety regulators and explosives handbooks, and equipment technical pages, spare parts catalogues, procurement documents and published patents. The GB/T 23894-2009 text itself is not available for online reading, because it adopts an ISO text under copyright, so a clause number should not be cited without the document in hand. The 2024 series of plain bearing standards covering steel-backed cast copper alloy, copper alloy to steel back, lead-free copper alloy bimetal and long fibre wound constructions were issued in 2024 and took effect on 1 May 2025.
Points that remain open
| Item | Status | How this page handles it |
|---|---|---|
| Graphite grade, fixed carbon content, and graphite type, whether electrolytic, moulded or filler treated | Not confirmed against a published standard | Not stated. The graphite is described by function and area fraction only |
| Composition of the solid lubricant grades referenced as SL1, SL2 and SL4 | Not confirmed from a source that can be cited | Only the published designation and the published statement that the values apply when that lubricant is used |
| Original equipment spare parts manuals and mineral processing journal papers | Not obtained | Positions marked Documented rest on equipment technical pages, parts catalogues, procurement documents and patents. These establish that the configuration exists, which is a narrower claim than widespread installed use |
13What to confirm before ordering
Each item below changes the material selection or the quotation. A print of this list, marked and returned with the enquiry, is faster than a clarification cycle.
- Equipment type and duty: open pit, underground, mineral processing, conveying, drilling or auxiliaryRequired
- Motion type: continuous rotation, reciprocating, or pivoting oscillationRequired
- Working speed in r/min and the resulting sliding speed in m/sRequired
- Cycle frequency in movements per minute, and whether impact is presentRequired
- Measured journal diameter and working length, as distinct from the housing boreRequired
- Measured journal hardness in HB or HRC, and the surface roughness RaRequired
- Radial load in kN or tonnes, and how it is distributed along the lengthRequired
- Whether an axial force is present, and whether its direction is fixedStructure type
- Continuous working temperature rangeRequired
- Medium: abrasive particles present, and whether acidic mine water is contacted, with the pHRequired
- Whether ammonium nitrate or a nitrate based explosive is contactedSafety
- Whether the position is in a methane or coal dust explosive hazard zoneLubrication
- Relubrication access: whether the position can be greased, and how long a shutdown takesRequired
- Whether a split installation is neededStructure type
- Base alloy and UNS number preference, if the order specifies oneQuotation
- Lead content restrictions under the destination market regulation or the customer specificationCompliance
- Acceptance criteria and the method of judgement, and whether typical values are acceptable in place of minimum requirementsCommercial
- Whether the order may refer to the standard in force at the delivery date, given the revision in progress on the reference standardCommercial
Send these details with your enquiry
Jiaxing VIIPLUS International Co., Ltd — VIIPLUS SOLUTIONS. Custom part sizes from 1.5 mm to 360 mm; standard bush diameters 6 to 300 mm with wall thickness 0.5 to 2.5 mm. Prototyping and small batch production with a low minimum order quantity, and stock availability across several designs and materials for immediate dispatch.
Enquiries: viiplus@viiplus.com · Overseas sales: tiffany@viiplus.com · Tel +86 573 84499350 · WhatsApp +86 182 5838 6757
Working hours 09:00 to 15:00 Beijing time. Payment by T/T. Packing in export cartons, wooden pallets or wooden cases, shipped by sea, train or air. Export to over 30 countries across Europe, the Americas, Japan and other regions.
On cost reduction claims
Our engineering support programme is designed to extend bearing service life and reduce the total cost of a bearing position, with cost reductions of up to 40 percent. This is an upper limit rather than a typical or assured saving, and the actual outcome depends on the duty, the size and the material previously used. It is not a warranty of any saving.
14Frequently asked questions
Is a solid-lubricant bronze bushing suitable for continuous rotation in mining equipment?
Usually not. For a tin bronze base the published maximum dry sliding speed is 0.40 m/s and the published dry PV limit is 1.00 N/mm²·m/s, and continuous rotation at working speed normally exceeds the speed limit. Rolling bearings or cast bronze bushes with a designed oil film are used instead. The exception is a continuous rotating position at very low sliding speed where periodic lubrication is not possible.
Can I use the maximum pressure rating and the maximum sliding speed at the same time?
No. They are independent limit values and cannot be combined. For a tin bronze base, 15 N/mm² multiplied by 0.40 m/s gives 6.0 N/mm²·m/s, six times the published PV limit of 1.00 N/mm²·m/s, so the PV product governs. At 15 N/mm² the permitted sliding speed is 0.067 m/s; at 0.40 m/s the permitted pressure is 2.5 N/mm².
What does the JDB or JFB designation mean in bronze bushing nomenclature?
JDB and JFB are trade and manufacturer designations, not structure types defined by GB/T 23894-2009. That standard defines four structure types instead: straight sleeve, flanged sleeve, thrust washer and slide plate. Some manufacturer catalogues write the same four as WQZ, WQZD and WQP. The numeric suffix after JDB indicates the base material, not a performance grade, and the prefix does not indicate a copper base. For an order, state the standard, the structure type, the base alloy with its UNS number, the dimensions, and the lubrication and fit requirements.
Can copper alloy bushings be used in the explosive path of a blasting vehicle?
No. Copper and copper alloys are excluded from equipment that contacts ammonium nitrate, because copper with ammonium nitrate can form tetraamminecopper nitrate, a compound sensitive to impact. Blasting and mixing equipment for ammonium nitrate based explosives uses non-copper materials such as stainless steel, cast iron, polyacetal, PTFE or aluminium, with the bearing and drive components located outside the mixer and dust accumulation prevented. This is a safety requirement and is not decided on load capacity.
Do the values on this page apply to my specific part number?
No. The values on this page are typical values published for this product class in bearing industry technical documentation, and they are shown with the source basis for each row. They are not assured minimum values for an individual part. VIIPLUS issues the applicable test report and inspection document against a specific order and drawing, so the values that apply to your part number are the ones in that report.
Metal Bushing (Lubricated Metal) -Self-Lubricating Bushing Materials
Bushings are specialized, self-lubricating metal components widely utilized across various industries due to their durability and low maintenance requirements. Self-lubricating metal bushings are engineered to function without additional lubrication in numerous applications, thereby minimizing maintenance needs. These bushings are available in various series and configurations, such as flanged bushings and split bearings, to meet specific application requirements.
Metal-Polymer Anti-Friction Plain Bearings
Metal-Polymer Composite Self-lubricating Bushing Material
Steel Back + Porous Bronze Sinter + PTFE
