C86300 / SAE 430B manganese bronze bushings

When to use C86300 – and what it demands in return

The alloy for positions where the specific load is at or above the limit of tin bronze and the movement is slow or intermittent: bucket and boom pins on large excavators, crane and slewing bushes, press linkage pins, crusher toggle and eccentric bushes, heavy gate bushes, thrust washers under shock. Its 427 N/mm² yield strength means the bush does not flow or brinell under impact the way a 65 HB tin bronze does, and its 225 HB gives the longest life against abrasive wear when the grease is clean.

It demands: a hardened shaft – 300 HB minimum, ground – because the bush is as hard as an unhardened shaft and would wear it; clean lubricant, since it does not embed grit; a generous running clearance (e8 rather than e7) because it does not conform; and a medium without warm saline or acidic water, in which the high-zinc alloy dezincifies. It machines slowly (rating 8) with carbide tooling, so it costs about twice a 660 bush and is not re-bored in the field as easily.

For your enquiry:For C86300: load or force and pin diameter, shaft hardness, movement and how the position is greased.

Design notes for C86300 bushings

Wall thickness can be thinner than for tin bronze at the same load thanks to the yield strength, but keep the ISO 4379 walls for the press fit – a thin hard bush cracks when pressed into an out-of-round housing. Chamfer the housing, press with a mandrel or shrink-fit; check the bore after fitting because the alloy closes less than tin bronze (higher modulus, 105 GPa).

Running clearance: e8 shaft or 0.15 – 0.25 % of the diameter, more for hot positions (expansion 21.2 × 10⁻⁶ /K, higher than steel). Grease: EP grease with solid additives (MoS₂ or graphite) for slow heavy pins, fed through a G3 circumferential groove under the nipple for oscillating pins or G4 figure-8 for rotation. Never run dry – there is no lead to save the surface.