JDB Graphite-Embedded Bushings in Mining Equipment
JDB Graphite-Embedded Bushings in Mining Equipment
High-Performance Self-Lubricating Bronze Bushing Solutions & Technologies. Minimize downtime, extend service life, and reduce costs for dynamic applications.
Plain bearing selection · Mining, crushing and bulk handling
JDB Graphite-Embedded Bushings in Mining Equipment: A Position-by-Position Selection Guide
1What decides whether a graphite-embedded bushing is suitable
Five findings carry most of the selection value. Each one is developed in the section referenced.
- The constraint is sliding speed, not load capacity. Above roughly 3 MPa contact pressure the allowable rotational speed is set by the sliding-speed limit and stops depending on shaft diameter, so on a pivot running at 10 to 40 MPa the load only decides how much wall thickness you need. (Section 5)
- Oscillating and rotating positions are calculated differently. A pivot has no steady rotational speed; it has an end-point speed, and for most heavy pivots that value is far below the limit. (Section 5)
- Load direction has to be established before anything else. The body carries the load and the plugs only lubricate, so the plug pattern has to run parallel to the direction of motion. If the direction is not known, a larger size does not fix the problem. (Sections 6 and 9)
- Abrasive contamination, not load, is what ends the life in mining. The plug grooves are where contamination collects, and once fines compact in a groove the transfer film cannot be replenished. Sealing design comes before material choice. (Sections 6 and 8)
- Two exclusions are not engineering choices. Positions that may contact explosives, and large-diameter continuously rotating positions, are not released by a load check. (Section 7)
2What the designation means, and which standard covers it
2.1 JDB is a trade designation, not a standard designation
These bushings are sold under several names: graphite-embedded bushing, solid-lubricant bushing, self-lubricating bushing, oilless bushing, and in Chinese and export trade, the JDB prefix. JDB does not appear in ISO 19259:2021 or in JIS B 1586, and the published JDB-1 through JDB-5 grade tables differ between suppliers. A grade table that reads differently on two suppliers’ websites cannot be used for ordering or for acceptance.
The portable way to specify this product is three elements rather than one code: base alloy grade, solid lubricant type, and structural form. That formulation survives a change of supplier, a change of plant, and an audit.
2.2 The four forms of self-lubricating bearing, and where this one sits
The four-type classification comes from the scope note of ISO 20054:2016, reproduced in the identical-adoption Chinese standard GB/T 39431-2020: “In the solid lubricant bearing among self-lubricating bearings there is a solid type, a coated type, an embedded type and a dispersed type, which is specified by this document.” The four forms differ in where the lubricant sits and therefore in how load is carried, so mixing the names leads directly to wrong selection.
| Form | Where the lubricant sits | Load path | Direction sensitivity | Governing standard |
|---|---|---|---|---|
| Embedded This product |
Discrete plugs or machined grooves, pressed into the body | Carried entirely by the metal body; the plugs supply film only | Strong. Concentrated loading of the plug zone is not permitted | GB/T 23894-2009; ISO 19259:2021; JIS B 1586 |
| Dispersed | Distributed through the whole material, powder-metallurgy formed | Lubricant phase and load-bearing phase mixed in the same section | Near-isotropic; load may be carried in any direction | ISO 20054:2016 / GB/T 39431-2020 |
| Solid / integral | Solid lubricant within a single composite material | One material carries the load | Isotropic | Material specification rather than a bearing standard |
| Coated | Dry-film lubricant coating on a machined surface | Substrate carries; coating reduces friction | Coating is vulnerable to impact and temperature cycling | Coating system specification |
| Oil-impregnated sintered | Stored in the pore network of a sintered skeleton; squeezed out under load, drawn back in at rest | Porous skeleton carries; impact capacity below a dense casting | Isotropic | ISO 2795:2020; GB/T 2688-2012, GB/T 18323-2022; ASTM B438, ASTM B439 |
Table 2.1 — The four self-lubricating bearing forms, and the separate oil-impregnated sintered family. The classification source is the scope note of ISO 20054:2016 and its identical adoption GB/T 39431-2020. Oil-impregnated sintered bearings rely on pore-stored oil rather than a solid lubricant, and are a different product class, not an alternative name for this one.
2.3 Standards that cover this product, and two that do not
| Standard | Title | What it covers | Status |
|---|---|---|---|
| GB/T 23894-2009 | Plain bearing — Copper alloy bearing with solid lubricant | Structural types, basic dimensions, technical requirements and test methods for copper alloy bearings with embedded solid lubricant. Structural types are the straight sleeve and flanged sleeve, derived from GB/T 18324, plus thrust washers and wear plates | Current in China. Revision plan 20254218-T-604 will widen the base material scope to metallic bases and align with ISO 19259:2021 |
| ISO 19259:2021 | Plain bearings — Bearings with embedded solid lubricants | The international specification for this product type. Edition 2, published 2021-10, superseding ISO 19259:2015 | Published. Only the scope statement is quoted on this page; numeric clauses are held in the purchased document |
| JIS B 1586 | Plain bearings — Bearings with embedded solid lubricants | The Japanese standard for the same product family | Confirm the current year and its relationship to ISO 19259 in the JISC database before citing it in a contract |
| ISO 3547 | Plain bearings — Wrapped bushes (Part 4: Materials) | Wrapped bushes, not this product | Current. Frequently misquoted as an oil-impregnated or embedded-lubricant standard |
| ISO 2795:2020 GB/T 2688-2012 GB/T 18323-2022 |
Plain bearings — Sintered bushes — Dimensions and tolerances; Plain bearing — Technical specification of powder metallurgy bearing; Plain bearings — Sintered bushes — Dimensions and tolerances | The oil-impregnated sintered family | Current |
Table 2.2 — Standards mapping. A repeated reference to “GB/T 19749” for oil-impregnated bearings is incorrect: that number is a standard for coupling capacitors and capacitors for power systems, in the IEC 60358 series, and has no bearing content. The correct references for the oil-impregnated sintered family are the ones listed above.
3Base alloy grades, and what each one changes
The body carries the load, so the base alloy sets the compressive and impact capacity, the heat rejection, and how the bearing behaves at temperature. The plug material sets the friction and the operating range. Changing the base alloy does not change the sliding-speed limit; changing the plug material does change the range.
| UNS grade | Common name | Composition, % (CDA) | Density g/cm³ | CTE ×10⁻&sup6;/°C | Thermal cond. W/m·K | Typical application in this product |
|---|---|---|---|---|---|---|
| C86300 | Manganese bronze, also called high-strength yellow brass. A Cu-Zn-Al-Mn-Fe brass, not a tin bronze | Cu 60–66 / Zn 22–28 / Al 5.0–7.5 / Mn 2.5–5.0 / Fe 2.0–4.0 / Pb 0.20 max / Sn 0.20 max / Ni 1.0 max | 7.83 | 21.6 | 35.5 | The mainstream base for graphite-embedded bushings in heavy mining duty. Highest tensile and yield strength in this group, with the highest impact values; welds poorly |
| C95500 | Aluminium bronze, Cu-Al-Fe-Ni | Cu 78 min / Al 10.0–11.5 / Fe 3.0–5.0 / Ni 3.0–5.5 / Mn 3.5 max | 7.53 | 16.2 | 41.9 | Wet, slurry and corrosive-water positions, and where the base is heat-treated. Welds and machines well. Heat-treated condition reduces elongation, which is the cost of that route |
| C95400 | Aluminium bronze | Cu 83 min / Al 10.0–11.5 / Fe 3.0–5.0 / Ni 1.5 max / Mn 0.50 max | 7.45 | 16.2 | 58.7 | As above, with better heat conduction. The preferred base where a heat-treated body and a welded repair are both wanted |
| C93200 | Leaded tin bronze, SAE 660 | Cu 81–85 / Sn 6.3–7.5 / Pb 6.0–8.0 / Zn 1.0–4.0 / Ni 1.0 max | 8.91 | 18.0 | 58.2 | Long-established for crusher toggle seats. The lead content is material to specification and is covered in A.5 |
| C90300 | Tin bronze, Navy G, SAE 620 | Cu 86–89 / Sn 7.5–9.0 / Zn 3.0–5.0 / Pb 0.30 max / Fe 0.20 max / P 0.05 max (1.5 max for continuous castings) / Ni 1.0 max | 8.8 | 18.0 | 74.8 | Lower-load positions where a low-lead tin bronze is preferred, for example wear plates in dry bulk |
Table 3.1 — Base alloy grades, with composition and physical properties from the Copper Development Association alloy database (alloys.copper.org). Mechanical properties are published by casting method and temper, and a hardness figure quoted without its casting method is not usable. The comparison in the text rests on the sand-cast figures: C86300 is published at 110 ksi minimum tensile, 60 ksi minimum yield at 0.5 % extension, 18 % typical elongation and 225 HB typical, against C95500 at 90 ksi minimum tensile, 40 ksi minimum yield, 12 % typical elongation and 195 HB typical. Compressive strength at 0.1 in. set per inch orders differently: C95500 120 ksi, C95400 100 ksi, C86300 97 ksi, C93200 46 ksi, so C86300 is not the highest on that measure. C90300 is published at 0.001 in. set per inch instead, and the two measures are not interchangeable. Casting specifications for these grades, by casting method and by alloy family, are listed in A.6. Expansion and conductivity are converted from the source values in ×10⁻&sup6;/°F and Btu/(ft·h·°F) to the SI units shown. Identify C86300 by its UNS number; regional Cu-Zn-Al-Mn-Fe nominal designations are not interchangeable on a drawing.
How the base alloy changes the engineering answer. C86300 and C95500 differ in ways that matter on a mine site. Manganese bronze gives the higher tensile and yield strength and the higher impact values, and it is the right default for a dry, dusty, shock-loaded pivot. Aluminium bronze forms a dense oxide film, welds, machines, and conducts heat noticeably better, and it is the better base for standing water, slurry or a corrosive atmosphere. Manganese bronze has the higher thermal expansion coefficient, so a hot running clearance closes further. Neither change moves the sliding-speed limit, which is set by the plug and the counterface.
4Working limits and how they are qualified
| Parameter | Dry service, graphite plug | Grease-lubricated service | Basis for these figures |
|---|---|---|---|
| Allowable PV | 1.5 MPa·m/s | 2.8 MPa·m/s | Typical industry design practice. Not published in ISO 19259:2021, and not in ASTM copper-alloy casting specifications, which cover composition, mechanical properties and test methods rather than duty limits |
| Allowable sliding speed | 0.5 m/s | 2.5 m/s | As above, for a high-strength brass base with a graphite plug |
| Allowable dynamic / short-term static load | 120 / 300 MPa | same | Supplier-published indicative figure for a high-strength brass base. Varies significantly with base alloy: an aluminium bronze base is higher, a tin bronze base lower. Indicative value, not a firm minimum requirement |
| Operating range, graphite plug | −40 to 400 °C, derated in service | — | Typical industry range. Graphite oxidises progressively in air above a few hundred degrees Celsius, so the upper figure needs derating against load, speed and heat removal |
| Operating range, fluororesin plug | −40 to 80 °C | — | Typical industry range for a fluororesin plug. A narrower window than graphite, and the reason a fluororesin plug is chosen for submerged or corrosive duty |
| Mating pin surface roughness | Ra 1.6 µm or better | — | Reported industry practice. Confirm the figure and its context against ISO 19259:2021 in the purchased document before writing it into a specification |
| Mating pin hardness | Confirm from measured values on the actual pin | Published practice ranges differ across sources, from a lower figure stated in HRC to a higher figure stated in HBW. These are not interchangeable and there is no single default; see Section 9 | |
| Housing fit | Transition fit for a cylindrical sleeve, with anti-rotation provision; interference fit for heavy duty | Reported industry practice. Specific fit designations are held in the purchased ISO 19259:2021 document and are not reproduced here | |
| Minimum wall to retain the plug | Cylindrical sleeve: 3 mm or more. Flanged: a stepped series of plate thicknesses | Reported industry practice. Confirm against ISO 19259:2021 in the purchased document | |
Table 4.1 — Working limits for embedded graphite bearings, with the basis of each figure stated. Where a figure is described as typical industry practice or as supplier-published indicative data, it is indicative rather than a firm minimum, and is not an acceptance criterion. Where a figure would come from ISO 19259:2021, that value is held in the purchased standard and is not reproduced here.
Two different kinds of PV number exist, and they are not interchangeable. A PV value of the order of 15 MPa·m/s appears in equipment-maker literature for cast tin bronze bearings, where the whole cast body carries the load. A value of 1.5–2.8 MPa·m/s refers to a system that includes a solid lubricant and operates differently. A PV figure quoted without naming the material system and the lubrication condition is not usable in a specification, and a drawing that mixes the two will be challenged.
The same caution applies to the temperature and fit figures. A value appears in circulation attributed to GB/T 23894-2009 — dry PV 1.65, greased 3.5 to 3.8, dynamic load 100 MPa, static 250 MPa, and a rocking test figure — and those numbers could not be traced to the published text of the standard. They are second-hand transcriptions and are not used on this page. Buy the standard and replace the affected rows with the values from the document itself.
5The sliding-speed screen: the calculation that settles most selections
Divide the allowable PV by the allowable sliding speed and the crossover contact pressure falls out:
pcrossover = PVmax / vmax = 1.5 / 0.5 = 3.0 MPa
Above about 3 MPa contact pressure, the rotational speed is limited by the sliding-speed ceiling and that ceiling no longer depends on shaft diameter. For a mining pivot running at 10 to 40 MPa, the selection therefore reduces to two numbers: the pin diameter and the pin speed, with the result taken from the table below.
| Pin diameter | Maximum rotational speed at 0.5 m/s | Check | What this means in practice |
|---|---|---|---|
| Ø100 mm | 95.5 r/min | 0.50 m/s | Most oscillating pivots fall inside this; rotating positions still need checking |
| Ø150 mm | 63.7 r/min | 0.50 m/s | The usual upper band for a heavy oscillating pivot |
| Ø200 mm | 47.7 r/min | 0.50 m/s | Close to the cycle rate of a haul-truck hoist; needs a real calculation |
| Ø250 mm | 38.2 r/min | 0.50 m/s | A large-diameter slow position; confirm end-point speed rather than rpm |
| Ø300 mm | 31.8 r/min | 0.50 m/s | Crusher eccentric bushing class. At 20 r/min the speed is inside the limit, but the forced-oil film arrangement is not substitutable |
| Ø450 mm | 21.2 r/min | 0.50 m/s | Very low ceiling for a large-diameter rotating position |
Table 5.1 — Rotational speed ceiling at a sliding speed of 0.5 m/s, from n = 60 · vmax / (π · d). Each entry was recomputed independently and checked back through v = π · d · n / 60. The underlying 0.5 m/s is the typical value from Table 4.1, not a standard-published limit.
5.1 Oscillating positions use end-point speed, not rpm
A pivot has no steady rotational speed. Use the end-point speed instead:
v = π · d · f · θ / 60 — f in cycles per minute, θ in radians per cycle.
For a heavy pivot on a mine site, f commonly falls between 6 and 15 cycles per minute and θ between 60° and 120°. Worked examples, all well inside the 0.5 m/s limit:
| Pin diameter | Cycles per minute | Sweep angle | End-point speed | Against the 0.5 m/s limit |
|---|---|---|---|---|
| Ø250 mm | 8 | 90° | 0.164 m/s | Inside, with margin |
| Ø200 mm | 10 | 120° | 0.219 m/s | Inside, with margin |
| Ø300 mm | 6 | 90° | 0.148 m/s | Inside, with margin |
| Ø150 mm | 12 | 90° | 0.148 m/s | Inside, with margin |
Table 5.2 — End-point speeds for representative heavy pivots. These are illustrative combinations of diameter, cycle rate and sweep angle, not measurements taken from any particular machine. The conclusion holds generally: a heavy oscillating pivot is usually far inside the speed limit, which is why this product ends up in that position class.
5.2 Where the limit reverses
A cone crusher eccentric bushing at Ø300 mm and 20 r/min gives 0.314 m/s, which is inside the limit, and it is still the wrong answer. The duty is continuous rotation combined with very heavy load and grinding slurry, so frictional heat has to be removed continuously and a solid lubricant film cannot carry that thermal duty. A pressure-fed hydrodynamic film is not a substitute to be traded away at a convenient price.
6Position matrix: 46 equipment positions across mining, crushing and bulk handling
Fit symbols: Recommended heavy oscillating or reciprocating duty where greasing is difficult and contamination can be controlled by sealing; Conditional usable once the duty, fit or contamination data is confirmed; Not suitable with the reason given in Section 7. Pin diameters and cycle rates are typical magnitude ranges for that class of equipment, not published data for any particular model.
| Assembly | Position | Motion and load | Environment | Form and base | Fit | Control point that decides it |
|---|---|---|---|---|---|---|
| A — Electric mining shovel, bucket-wheel excavator, and hydraulic mining excavator 20–50 t | ||||||
| Bucket wheel and bucket | Tooth pin and seat | High-frequency impact, one-way, in direct contact with ore | Ore, oil-bearing slurry | High-chrome cast iron or hardened steel seat | Not suitable | Abrasive erosion duty. A soft copper body is removed by design; wear resistance needs hardness and a hardfaced or carbided seat |
| Bucket wheel support arm | Support arm pivot | Oscillating, heavy, Ø250–450 | Windblown sand, rain | Straight or flanged sleeve, high-strength cast brass base | Recommended | A large-diameter slow oscillation. Check the end-point speed, not the rotation rate |
| Boom elevation and crowding | Main boom base pivot | Oscillating, extreme load, large sweep angle | Sand, occasional impact | Straight sleeve, extended length-to-diameter, high-strength brass or aluminium bronze | Recommended | Single-point downtime cost is high and greasing access is poor |
| Stick to bucket linkage | Stick pin and seat | Oscillating, heavy, Ø150–300 | Sand, slurry | Straight sleeve, high-strength cast brass | Recommended | Fit a wiper ring. Once grit covers the transfer film it damages the pin |
| Bucket cylinder | Cylinder rod eye | Oscillating, heavy with reversing impact | Sand, oil film | Spherical self-aligning bushing, steel-backed bronze with graphite | Conditional | A spherical self-aligning form is needed to absorb alignment mismatch |
| Undercarriage | Track roller and idler bore | Continuous rotation, medium, Ø120–300 | Mud, sand | Rolling bearing with mud seals | Not suitable | This is a sealing and rolling-element life problem. A conversion needs a complete sealing package |
| Undercarriage | Balance beam pivot | Oscillating, heavy, Ø200–400 | Sand | Straight sleeve, high-strength cast brass | Recommended | Hard to reach for service, and the change window is outside the assembly line |
| Rod handling | Rod dropper or changer pivot | Oscillating, medium, Ø60–150 | Rock dust | Steel-backed bimetal or oil-impregnated | Conditional | Higher cycle rate; the PV value needs checking |
| B — Mining haul truck 90–140 t and underground haul truck | ||||||
| Hoist | Body hoist hinge and trunnion | Oscillating, heavy with dump impact, Ø200–400 | Sand, mud, impact | Straight sleeve, extended length, high-strength brass or aluminium bronze | Recommended | A high-value conversion on the criterion in Section 9: heavy oscillation, poor access for grease, and a high cost per stop. Pin bending and bore crushing are the governing failures |
| Hoist | Front lift cylinder eye and front beam pivot | Oscillating, heavy, large sweep angle, Ø150–280 | Sand, rain, mud | Spherical self-aligning bushing, steel-backed bronze | Recommended | Very little maintenance access |
| Hoist | Front lift cylinder ball joint | Oscillating, heavy, large sweep angle | Sand, mud | Spherical self-aligning, steel-backed bronze | Recommended | Sand ingress is the main initiator of failure |
| Steering | Steering king pin | Reciprocating, intermittent impact, Ø60–120 | Mud, rain | Nylon, oil-impregnated, or bimetal | Conditional | Nylon absorbs water and swells. Confirm the side load |
| Suspension | Suspension and spring seat pin | Oscillating with vibration, heavy, high-frequency small stroke | Mud, corrosive water | Tin bronze or aluminium bronze base | Conditional | Confirm lateral acceleration and the corrosive medium |
| Driveline | Wheel hub end and drive axle | Continuous rotation, heavy, 300–600 r/min | Mud, rain | Tapered roller or ball bearing with seals | Not suitable | Over the speed limit, and a sealing and rolling-element problem |
| Driveline | Driveshaft slip joint and Cardan joint | Rotation with high-frequency oscillation, torque shock | Mud, corrosive water | Cardan joint cross with grease seal | Not suitable | Torsional stiffness and sealing govern |
| C — Drilling, blasting and loading | ||||||
| Top-hammer and down-the-hole drill | Boom base and intermediate pivot | Oscillating, heavy, Ø100–250 | Rock dust, water mist, confined space | Straight sleeve, high-strength brass or aluminium bronze | Recommended | A high-value conversion underground on the criterion in Section 9, where access for grease is worst |
| Drill | Feed beam pivot and mast foot | Oscillating, medium to heavy, 20–80 cycles per minute | Rock dust, water | Straight sleeve, high-strength cast brass | Recommended | High cycle rate. Check the end-point speed at this frequency |
| Drill | Rock drill cradle and rod guide | Reciprocating, high-frequency impact, medium | Rock dust, water mist | Wear-resistant polymer slide, or cast tin bronze | Conditional | High impact spectrum. A guide slide is often the better answer than a bushing |
| Drill and crane | Sheave and rope guide pulley | Continuous rotation, medium, Ø150–500 | Rain, rock dust | Straight sleeve at low speed, tin bronze or aluminium bronze | Conditional | Rope speed is the criterion, not shaft speed. A high rope speed needs recalculating |
| Down-the-hole drill | Feed cradle | Reciprocating, impact, medium to heavy, Ø60–120 | Rock dust, mud | Steel-backed bimetal | Conditional | Has to match the rock drill vibration spectrum |
| Top-hammer bit joint | Button bit connection and threaded joint | Impact with thread locking, hundreds of impacts per minute | Rock dust | Alloy steel or hard alloy | Not suitable | Locking torque and fatigue strength govern. A plug reduces the effective section |
| Bulk loader, loading vehicle | Auger and metering pump housing | Rotation with augering, continuous, 60–300 r/min | Direct contact with ammonium nitrate or emulsion | Stainless steel, cast iron, or non-metallic | Not suitable | Safety exclusion. See Section 7, item 2 |
| Explosive system | Hose reel guide roller | Rotation and winding, 30–120 r/min | Adjacent to the explosive path | Steel-backed PTFE or engineering polymer | Not suitable | Requires physical isolation from the explosive path, or the assembly changed to non-copper |
| Explosives handling | Magazine hinge | Reciprocating, light, intermittent | Explosive contact risk | Stainless steel or non-metallic | Not suitable | Non-copper in all magazine and explosive-adjacent locations |
| D — Crushing and grinding | ||||||
| Jaw crusher | Toggle seat and moving jaw pivot | Oscillating, high-pressure impact, 5–15 cycles per minute | Heavy dust, tramp metal | Straight sleeve for the seat, spherical for the plate; high-strength brass or cast tin bronze | Conditional | Leaded tin bronze is long-established practice here. A conversion has to account for the impact peaks |
| Cone crusher | Socketing liner and spherical seat | Oscillating, heavy, large sweep angle, spherical Ø400–1200 | Dust | Spherical self-aligning, high aluminium bronze or hardfaced liner | Conditional | Aluminium bronzes may contain a hard phase. Check whether a replaceable liner is required |
| Cone crusher | Eccentric bushing, inner and outer | Continuous rotation with oscillation, extreme load, Ø300–1200, 60–300 r/min | Dust, oil mist | High-leaded tin bronze with forced oil | Not suitable | Both speed and heat balance exceed what a solid lubricant system can carry. See Section 7, item 1 |
| Ball mill, SAG mill | Trunnion journal | Continuous rotation, extreme load, Ø800–1800, 5–20 r/min | Grinding slurry, corrosive water | Babbitt lining with hydrostatic oil film | Not suitable | A fluid-film solution is not substitutable here |
| Vibrating screen | Exciter housing joint | Rotation with high-frequency micro-amplitude, medium, 900–1200 r/min | Dust | Steel-backed bimetal for the housing seat | Conditional | The housing seat can take an embedded bushing; the exciter shaft itself takes a rolling bearing |
| Classifier | Shaft sleeve and screw bushing | Continuous rotation, medium, Ø80–200, 30–120 r/min | Wet slurry | Straight sleeve, dry section only, tin bronze or aluminium bronze | Conditional | The wet section needs flushing and drainage confirmed. Slurry in the groove ends the life |
| Cyclone and piping | Feed inlet liner | Sliding contact with material, high-velocity erosion | High-solids slurry | High-chrome cast iron, rubber, or ceramic | Not suitable | Slurry packs the plug grooves. See Section 7, item 4 |
| Feeder conveyor | Idler and bend roller bearing seat | Continuous rotation, light, Ø25–89, 100–600 r/min | Dust, impact from falling material | Deep groove ball or tapered roller, grease-sealed | Not suitable | A rolling-element rating life and seal class question |
| E — Bulk handling | ||||||
| Belt conveyor | Idler bearing | Continuous rotation, light, 100–600 r/min | Open dust, rain | Rolling bearing selected to L10 life and seal class | Not suitable | Numerous on site, and a rolling-element life and seal-class question rather than a bushing question |
| Belt cleaner | Cleaner arm and blade pivot | Oscillating, medium | Dust, mud | Straight sleeve, high-strength cast brass | Recommended | Greasing this position by hand is impractical |
| Discharge | Tripper and plow pivots | Oscillating, medium to heavy, 20–60 cycles per minute | Dust, material abrasion | Straight sleeve, high-strength cast brass | Recommended | Oval pin bores and plow bottoming are the governing failures |
| Pull-cord switch | Switch sheave and guide roller | Continuous rotation, light, 60–200 r/min, Ø40–120 | Dust, open air | Oil-impregnated or bimetal | Conditional | Light duty, and a low-cost entry point for an embedded bushing |
| Chute and hopper | Liner slide | Planar sliding, heavy, full contact with material | Dry bulk or wet sticky bulk | High-chrome cast iron for wet, graphite-plugged wear plate for dry | Conditional | Dry bulk only. Wet sticky material sheaths over and destroys the friction pair |
| Stacker-reclaimer | Travel wheel bore | Continuous rotation, medium, 30–120 r/min, Ø150–350 | Sand, rain | Oil-impregnated or steel-backed bimetal | Conditional | Usable where the rail is kept clear of slurry. Confirm the sealing |
| F — Underground mining and ground support | ||||||
| Roadheader | Boom base pin | Oscillating, heavy, Ø200–400 | Rock dust, water inflow | Straight sleeve, extended length, high-strength brass or aluminium bronze | Recommended | Hard to reach for service. Bore crushing and pin bending are the governing failures |
| Roadheader | Cutter boom and loading joint | Oscillating with high-frequency vibration, heavy | Rock dust, water inflow | Steel-backed bimetal | Conditional | Underground units are usually already centrally lubricated. Recompute the actual duty first |
| Bolter | Boom pivot | Oscillating, medium, 30–100 cycles per minute | Damp, rock dust | Straight sleeve, high-strength cast brass | Recommended | High cycle rate underground, with poor access for grease |
| Ground support | Hydraulic cylinder eye | Oscillating, heavy, slow | Water inflow, mud | Spherical self-aligning, steel-backed bronze | Recommended | Spherical form. Rusting seizure is the main failure |
| Underground loader, LHD | Articulation hitch pin | Oscillating, heavy with side load, Ø150–300 | Mud, high humidity, corrosive water | Straight sleeve, aluminium bronze base for acid water | Recommended | Clearance over limit drives tyre wear directly |
| Underground loader, LHD | Bucket pin and lift cylinder eye | Oscillating, heavy, slow | Mud, water inflow | Straight sleeve or spherical, aluminium bronze base | Recommended | Aluminium bronze base where water is acidic |
| Underground processing plant | Fixed pivots, wet section | Oscillating, medium, slow | Standing water, corrosive water | Straight sleeve, aluminium bronze with fluororesin plugs | Conditional | Leaded tin bronze holds no advantage here. A graphite plug in standing water carries a galvanic-corrosion risk, so use a fluororesin plug |
| Backfill and grouting | Pump mount and pipe guide roller | Rotation with oscillation, medium | Cement slurry | Guide roller, steel-backed PTFE or wear-resistant polymer | Conditional | Only where the roller is fully isolated from the slurry. Set grout seizes the shaft |
| G — Reliability, repair and assembly practice | ||||||
| Any pivot | Bore repair by sleeving | Worn bore, body otherwise sound | As the position | Thin-wall steel or bronze liner | Recommended | Ream the bore and fit a thin-wall liner. This converts a worn dimension into a standard dimension, with a controllable lead time and cost |
| Priority order for a first conversion | 1. Body hoist hinge 2. Front lift cylinder ball joint 3. Underground LHD articulation pin 4. Roadheader boom base pin 5. Belt cleaner and plow pivots | Heavy oscillation, greasing difficult, single-point downtime cost high | — | — | Recommended | The common feature across these five is the combination of heavy oscillation, difficult access for grease, and a high cost per stop |
| Fit and installation | Reported practice: transition fit for a cylindrical sleeve with anti-rotation provision, interference fit for heavy duty | — | — | — | — | Do not work the plug zone with a hammer. Use a chamfered guiding tool, or hydraulic or thermal shrink fitting. Measure the bore before and after fitting, and run in at low speed and low load to establish the transfer film |
| Mating pin | Confirm hardness from measured values | — | — | — | — | Do not default to the lower end of a published range. Roughness and the hardened layer have to match the liner, or hard particles scratch the transfer film during run-in |
Table 6.1 — Position matrix. Groups A to F hold 46 equipment positions; group G holds four entries on repair, installation and mating-part practice. Pin diameters and cycle rates are typical magnitude ranges for that class of equipment, used for a first-pass PV and end-point speed screening. They are not published data for any particular machine, and they have to be replaced with measured values before a quotation is issued.
6.1 The same matrix as a material choice
| Construction | Heavy oscillating pivot | Extreme pressure, low speed | Continuous rotation | Abrasive contamination | Wet or corrosive water | Explosives contact |
|---|---|---|---|---|---|---|
| Embedded, high-strength cast brass base | Yes | Yes | Cond. | Cond. | Cond. | No |
| Embedded, aluminium bronze base | Yes | Yes | Cond. | Yes | Yes | No |
| Embedded, fluororesin plug | Cond. | Cond. | Cond. | Cond. | Yes | No |
| Oil-impregnated sintered | Cond. | Cond. | Yes | Cond. | Cond. | No |
| Steel-backed bimetal composite | Yes | Yes | Yes | Yes | Cond. | No |
| Dispersed solid lubricant alloy | Yes | Cond. | Yes | Cond. | Cond. | No |
| Engineering polymer or composite | No | No | Cond. | Cond. | Yes | Yes |
| Rolling bearing | Cond. | Yes | Yes | No | Cond. | Yes |
Table 6.2 — Construction against duty class. The last two columns carry the argument of this table. A rolling bearing is excluded across the abrasive column and is one of only two options released for explosive contact, because contamination resistance and explosive compatibility are different kinds of constraint and one does not substitute for the other.
7Positions where this product is not the answer
Twelve cases come up repeatedly, and the first two are the ones most often applied wrongly.
| # | Position or situation | Why it does not work | What to use instead |
|---|---|---|---|
| 1 | Crusher eccentric bushing, mill trunnion journal, any large-diameter slowly rotating heavy position | Under continuous rotation, frictional heat has to be carried away continuously and a solid graphite film has no means of shedding it. At Ø300 mm and only 20 r/min the sliding speed reaches 0.314 m/s; combined with very heavy load and slurry, the body softens and the eccentricity goes out of alignment. This is not a question of whether the product can be used, but of the hydrodynamic film being irreplaceable at that diameter and speed | Keep the pressure-fed hydrodynamic arrangement: high-leaded tin bronze with an induced oil film, or forced circulation. At small diameters, a rolling bearing |
| 2 | Any position on a loading vehicle, bulk loader or explosives handling equipment that may contact the explosive | A safety exclusion, not an engineering option. Ammonium nitrate reacts with copper and copper alloys under damp conditions to form sensitive copper-ammonia compounds, and industry safety guidance excludes copper, copper alloys and zinc. Emulsion compatibility listings exclude copper and copper alloys on the same basis. A load check does not release this | Stainless steel, cast iron, or a non-metallic composite. Where isolation is not possible, the assembly changes to non-copper throughout |
| 3 | Top-hammer bit joints, rock drill impact positions, threaded locking parts | High-frequency impact with thread locking, where fatigue strength and locking torque govern. A plug opening reduces the effective section, and a solid lubricant film is crushed under impact | Alloy steel or hard alloy, with the thread and locking faces as originally designed |
| 4 | Cyclone feed inlets, slurry piping, wet classifier liners, wherever slurry enters the grooves | The grooves are lubricant reservoir space. Once they are packed with slurry, sand or grout and cannot be drained, the friction pair degrades from solid lubrication to hard-particle abrasion | High-chrome cast iron, rubber or ceramic liners. Or design flushing, drainage and an oil barrier first, then reassess |
| 5 | Conveyor idler seats, bend rollers, slew bearing interfaces | This is a rolling bearing question. It needs a calculable rating life and a replaceable seal class, not the removal of a lubrication point | Rolling bearing type by speed and impact, seal class by dust and rain exposure |
| 6 | Brake friction pairs and brake cylinders | Thermal capacity, friction coefficient and wet fade determine brake performance. A bushing does not perform that function | Design the brake assembly as an assembly |
| 7 | Tooth pins and seats in direct contact with ore | Abrasive wear needs hardness and particle erosion resistance. A soft copper body is removed by design and its life is measured in hours | High-chrome cast iron or hardened steel with a hard alloy tooth seat |
| 8 | Positions needing seal pressure retention, such as a piston rod guide or a gland follower | The function there is guiding and wiping. The design does not allow a friction pair and a running clearance, and a liner degrades guiding accuracy and seal lip behaviour | A piston rod guide combined with a wiper ring |
| 9 | Guide rollers and hot work rollers with a high temperature rise | A solid lubricant removes the lubrication limit, not the material temperature limit. A leaded tin bronze base enters a softening risk band in the region of 140 °C | Heat-resistant base with a higher-grade graphite, or a high-temperature-specific self-lubricating material |
| 10 | Food, drinking water and feed contact surfaces | Copper ion release and lead leaching from a leaded tin bronze are governed by food-contact regulation, which is outside the scope of this document | A food-contact-compliant material, or a non-copper alloy |
| 11 | Precision rotation, or mechanisms needing repeatable positioning | The transfer film is a sacrificial layer and is rebuilt at every start. Friction and torque during start-up are higher than in steady running, so repeatability is not stable | A rolling bearing or a fluororesin composite liner |
| 12 | Precision motions after a long stand-by period | During stand-by the transfer film degrades, and the first movement after a stop can be sticky, which is a hazard for a precision action | Retain grease lubrication and set a periodic movement regime |
Table 7.1 — Positions where a graphite-embedded bushing is not the answer, with the engineering reason and the alternative route.
8Failure modes that drive the selection decision
Ten modes account for most field returns. Modes F1, F2, F5, F6, F7 and F10 trace back to housing geometry, fit, length-to-diameter ratio, pin hardness and pin finish rather than to the bushing material itself, which is why a material upgrade alone often does not resolve them.
| # | Mode | What it looks like | What triggers it | Severity | Can bushing parameters avoid it |
|---|---|---|---|---|---|
| F1 | Brinelling, or crushing of the body | Plastic indentation in the loaded zone, loss of roundness | Static or impact load beyond the body yield; length-to-diameter ratio too small; housing misalignment causing single-sided loading | High | Partly: base alloy, length-to-diameter ratio, anti-rotation provision |
| F2 | Edge chipping at the groove mouth | The bronze lip lifts and curls into a burr, and the mouth opens out like a bell | Concentrated load aligned with the groove mouth; fitting without a chamfered guide; pin roughness out of specification | High | Partly: chamfer, groove diameter and pitch. Load alignment cannot be engineered away |
| F3 | Plug loss | A groove is empty or the plug has sunk, leaving a bare bronze band on the friction surface | Insufficient plug interference; impact; a tool levering a plug out during machining | High | Yes: graphite grade, groove diameter and depth, plug coverage |
| F4 | Debris packing | The groove mouth is filled and hardened with slurry or dried fines | Seal failure; reversing motion driving material in repeatedly; no wiper | Medium to high | Yes: groove orientation, pitch, and a drain path |
| F5 | Abrasive wear | Striations along the direction of travel, and a bright polished band on the pin | Solid particles entering the friction pair; particle hardness close to the body; load too high | High | Partly: base strength, plug coverage. Not fully avoidable |
| F6 | Seizure | A bright, blued friction surface with an adhered transfer layer, and a local lock-up | Film breakdown with PV beyond the limit; the transfer film did not establish; grease contaminating the graphite; thermal expansion closing the clearance | High | Yes: PV margin, plug coverage, length-to-diameter ratio |
| F7 | Spinning in the housing | Circumferential scoring on the outside diameter and rotation of the liner relative to the housing | Insufficient interference; poor housing roundness; thermal expansion mismatch; no anti-rotation feature | Medium to high | Yes: interference, anti-rotation provision |
| F8 | Cracking during fitting | Cracks visible at the groove mouth immediately after fitting, and the bore reduced by the press-in | Driving the part in by hammer blows; no guiding tool; uncontrolled press force; interference too high | High | Yes: material and bore finishing practice |
| F9 | Corrosion and dezincification | Verdigris-coloured or dark brown corrosion products, and a dezincified layer visible in a brass base | Damp slurry, standing water, sulphurous or chlorinated media; a graphite and steel couple in a damp medium, which is worse during long stand-by | Medium to high | Partly: base alloy and corrosion grade. The galvanic couple cannot be engineered away |
| F10 | Thermal seizure | The clearance closes while hot and the shaft cannot be withdrawn | Sustained high temperature with a high PV; a mismatch between the expansion of shaft and liner; running clearance not allowing for temperature rise | High | Yes: base alloy, fit, clearance |
Table 8.1 — The ten failure modes that most often drive a field return. If the five inputs named above are not available at the selection stage, a higher-grade material on its own often changes nothing, because the failure happens outside the bushing.
9Selection sequence and the data needed for a quotation
9.1 The sequence
- Start with the motion, not the load.Oscillating and reciprocating duty suits this product; check the end-point speed against Section 5. Continuous rotation: calculate the sliding speed first, and if it exceeds the limit, stop here. High-frequency impact: go to step 5 and work from the impact spectrum. Load does not enter the decision at this step.
- Then look at the environment.Where a grease path exists and someone actually uses it, converting to a solid-lubricant bushing removes a lubrication point and nothing more, which is not a reason to convert. Dust, slurry, water ingress and difficult access are where the product earns its place. At the same time, check the exclusions in Section 7, particularly explosives contact.
- Rank by access and cost of a stop.Order positions by greasing difficulty multiplied by the cost of a single-point stop, and start with the positions that combine the greatest greasing difficulty with the highest cost of a stop: the body hoist hinge, the front lift cylinder ball joint, the underground loader articulation pin.
- Confirm the mating parts.Take the measured pin hardness and roughness rather than a default. If roughness is out of limit or the pin is not hardened, the transfer film takes far longer to establish, and wear during run-in is higher.
- Fix the structural form.Plug or groove, plug coverage, groove orientation parallel to the direction of motion, length-to-diameter ratio, and whether a spherical self-aligning form is needed. If the load direction is not established, stop here and move to a steel-backed composite or a dispersed-lubricant alloy instead of specifying a larger size of this product.
- Apply the exclusions.Explosives contact, large-diameter continuous rotation, slurry entering the grooves, a position needing seal pressure retention, and excessive temperature rise. Any one of these reverses the decision, and the selection returns to step 2.
9.2 The data needed before a material recommendation
Each of the following changes the recommendation or the quotation. Items 1, 2, 5 and 6 are the ones that most often do.
10FAQ
Is a JDB designation an ISO or JIS designation?
No. JDB is a trade designation used in Chinese industry and in export marketing, and it does not appear in ISO 19259:2021 or in JIS B 1586. Published JDB-1 through JDB-5 grade tables also conflict between suppliers, so they are not a reliable specification basis. Specify the base alloy grade, the solid lubricant type and the structural form instead.
What is the maximum PV value for a graphite-embedded bushing?
A commonly used design value for dry service is PV at or below 1.5 MPa·m/s with a sliding speed at or below 0.5 m/s. These are typical industry design-practice figures, not values published in ISO 19259:2021 or in ASTM copper-alloy casting specifications, and they are indicative values rather than firm minimum requirements. Confirm them against the test data for the specific grade and base alloy before writing them into a specification.
Why does sliding speed rather than load decide whether a graphite-embedded bushing is suitable?
Because the two limits are reached at different points. With PV at or below 1.5 MPa·m/s and sliding speed at or below 0.5 m/s, the crossover sits at a contact pressure of about 3 MPa. Above that pressure the speed limit governs the allowable rotational speed, and the allowable speed no longer depends on shaft diameter. On a mining pivot running at 10 to 40 MPa contact pressure, suitability is therefore decided by pin sliding speed.
Can graphite-embedded bushings be used in wet or corrosive environments?
A graphite plug in standing water or salt water can form a galvanic couple against a steel pin, and dezincification can affect a high-zinc brass base. For those conditions, use an aluminium bronze base, or a fluororesin plug instead of a graphite plug, and confirm the exposure with the material supplier. The operating range quoted for fluororesin plugs is narrower than for graphite.
How long does a graphite-embedded bushing last in mining service?
There is no published service life figure that can be applied to your duty, and any such figure quoted without a stated test condition is not usable. Replacement is judged on measured clearance and on the condition of the removed part, not on a calendar interval.
Do graphite-embedded bushings need maintenance?
They do not require scheduled re-greasing, which is the main reason they are specified. That is not the same as needing no upkeep. Periodic inspection remains necessary, because graphite plug loss, edge chipping, debris packing and seizure are all progressive, and they are visible at inspection but not from a distance. Some positions still need a grease path for other reasons.
Can a graphite-embedded bushing be used where explosives are handled?
Not where the component may contact ammonium nitrate or emulsion explosives. Ammonium nitrate reacts with copper and copper alloys under damp conditions to form sensitive copper-ammonia compounds, and industry safety guidance excludes copper, copper alloys and zinc from those positions. This is a safety exclusion, not a load-dependent engineering choice, and it is not released by a load check. It has to be confirmed by qualified personnel under the rules applying at the site.
Send us the duty and we will screen it
Give us the position, the pin diameter, the cycle rate and the sweep angle for an oscillating position or the rotational speed for a rotating one, the measured pin hardness, and what the position is exposed to. We will return the sliding speed, the contact pressure, the PV figure, the direction-of-load check, and a recommendation with the base alloy and plug type, together with the positions we would exclude and why.
We will also say when the answer is that this product is not right for the position, and what is.
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
