C86300 Manganese Bronze Bushings with Internal Grease Grooves

C86300 manganese bronze bushings are cast copper-alloy bushings specified for heavy loads at low sliding speeds, where a full hydrodynamic oil film cannot form. Internal grease grooves — circumferential rings, cross-drilled feed holes, or figure-8 patterns — hold lubricant at standstill and distribute it into the loaded arc during motion. This page covers what each groove pattern does, where these bushings are used, the published engineering data, and how to specify one on a drawing.

What C86300 manganese bronze is

C86300 (UNS C86300, SAE 430B) is a high-strength cast copper alloy strengthened by aluminium, iron and manganese. Despite the “bronze” trade name, the matrix is copper-zinc — metallurgically a high-tensile brass — and its strength class sits close to mild steel. It is non-heat-treatable: properties come from composition control and casting quality. It is supplied as continuous cast bar and tube (ASTM B505), centrifugal cast tube (B271) and sand castings (B584).

Low lead content (Pb ≤ 0.2 %) makes C86300 a practical choice where leaded bearing bronzes such as C93200 (7 % Pb) are excluded, including food-machinery and drinking-water-adjacent applications.

Why internal grease grooves matter

At low speed or under oscillation, the journal never builds a hydrodynamic film, so grease itself is the separator. Grooves are a distribution system: they hold a grease reservoir at standstill and move lubricant into the arc that actually carries load. A groove cut through the primary load arc interrupts the film and removes bearing area, so the pattern and its position are chosen from the motion type and load direction — not copied from habit.

Groove geometry in practice: width typically 8–12 % of the bore diameter and depth about half the width, with rounded edges; published ranges for industrial bores are 1.5–3.2 mm wide × 1.0–2.0 mm deep. The groove starts at the feed hole and stops short of the bushing ends so lubricant is not simply pushed out. For figure-8 grooves, published practice is 1.5–3 mm deep × 3–6 mm wide.

Where C86300 grooved bushings are used

Relubrication practice (starting points): excavator-class pins every 8–10 operating hours until fresh grease shows at both ends; press and index-table pivots weekly to monthly. Shorten intervals for joints that run hot, wet or in abrasive dust.

Engineering data — grease-lubricated, solid cast C86300

C86300 compared with other bearing bronzes

Specify C86300 when dynamic load exceeds roughly 15–25 N/mm² or shock is present, sliding speed stays at or below ~0.5–1.0 m/s, and a hardened shaft is available. Consider an alternative when the duty is continuous high speed (hydrodynamic or rolling-element design), dry running without graphite plugs is required, maximum embeddability in abrasive dirt is the priority (C93700 / C93200), temperatures exceed 260 °C or the media is aggressive (aluminium bronze), or the duty is light and cost-sensitive (C93200).

Manufacturing and groove machining

Bushings are cast as continuous (B505), centrifugal (B271) or sand castings (B584), then CNC turned and bored to size. Internal grooves are cut with form tools on small bores, or CNC live-tool and 4th-axis spiral machining for circumferential, spiral and figure-8 patterns; cross-drill holes are located by jig to the load-direction datum marked on the drawing. The bore is finished to running clearance after pressing (ream or hone where specified). Every batch ships with a material test report covering composition and hardness.

How to specify on a drawing

• ID / OD / length with tolerances (bore H7 where finished after fitting; OD press fit per wall thickness);
• Groove pattern, width and depth, plus feed-hole diameter and angular position relative to load direction;
• Lubrication: grease type, fitting type, and any relief ports;
• Material certification: UNS C86300 to ASTM B505 / B271 / B584 with MTR;
• Mating shaft hardness and finish, housing material and tolerance;
• Quantity and any third-party certification required.

Maintenance practice that extends wear life

In pin-and-bushing joints, wear concentrates on the loaded arc, not the full bore. A widely used fleet maintenance practice is to press the pin out at scheduled intervals, rotate the bushing 180° so the unworn arc takes the load, and refit — spreading wear over a larger area of the bore. Treat this as maintenance practice to be validated against your duty cycle, not as an engineering guarantee.

FAQ

What is C86300 manganese bronze used for?

Heavy loads at low sliding speeds: excavator and crane pivots, hydraulic cylinder end mounts, bridge pins, steel-mill screw-down nuts, slow-turning crusher and mill positions, and press clamp bushings. Its 758 MPa minimum tensile strength and 380 MPa compression deformation limit suit shock and static loads that softer bearing bronzes cannot carry.

What is a figure-8 groove in a bronze bushing?

An internal grease channel of two intertwined spiral paths crossing at two diametrically opposite points (also described as two overlapping ovals meeting at a central feed hole). It keeps grease circulating into the arc that actually moves under oscillation, which is why it is specified for pivot and reciprocating duty rather than continuous rotation.

Why cross-drill a bronze bushing?

Cross-drilling connects an external grease source in the housing to an internal circumferential groove through the wall, so the joint can be regreased from a zerk without disassembly. It is used where grease access is poor — cylinder end mounts, bridge positions, marine fittings. The holes must be plugged or fitted, and positioned on the drawing relative to the load direction.

Is C86300 a bronze or a brass?

Metallurgically it is a high-tensile brass: zinc is the dominant alloying element (22–28 %), with aluminium, iron and manganese providing strength. The “manganese bronze” name persists because the alloy competes with true bronzes in bearing service. On drawings, always write the UNS/ASTM designation, not the trade name alone.

C86300 or C93200 — which bushing should I choose?

Choose C86300 when load and impact resistance dominate and speed is low; choose C93200 for general machinery at moderate loads and higher speeds, or when embeddability in dirty conditions matters more than strength. C93200 contains about 7 % lead, which excludes it from lead-restricted applications; C86300 is a low-lead alloy (Pb ≤ 0.2 %).

What PV limit applies to C86300 bushings?

For solid, grease-lubricated cast C86300 at low speed, typical published envelopes are 1.5–2.5 N/mm²·m/s, with some catalogs publishing up to ~3.25 for specific sizes and conditions. Always read PV together with the lubrication state and motion type — dry-running figures for graphite-plugged bushings are a different product family and cannot be substituted.

Can C86300 bushings run dry?

Solid C86300 is not intended for dry friction — without a lubricant film, galling risk is high. For dry or poorly lubricated duty, specify a graphite-plugged self-lubricating variant, which forms a solid transfer film and covers a different load-speed envelope.

What shaft hardness and finish do C86300 bushings need?

A hardened shaft — at least 200 HB (or 70–100 HB harder than the bushing) — with Ra ≤ 0.8 µm surface finish, tightened to Ra ≤ 0.4 µm for heavy loads. Running clearance is typically 0.025–0.040 mm per 25 mm of shaft diameter.

Can you machine custom grooves and supply to drawing?

Yes. Circumferential, cross-drilled, figure-8, spiral and axial patterns are machined to drawing, with feed holes located to your load-direction datum. Send the drawing, duty data and quantity for an engineering review; material test reports accompany every shipment and lead time is confirmed at quotation.

Request an engineering review

Send your shaft diameter, housing bore, duty parameters (load, speed, motion type, temperature, environment), groove drawing and quantity. Our engineers confirm the alloy, groove pattern and fits against your duty data before quoting — including cases where a different alloy or lubrication concept is the honest answer.

Typical figures on this page are published reference values from ASTM and CDA data sheets and industry engineering practice; they are not a warranty of performance in a specific application. Final selection is confirmed against verified duty data before order acceptance.