Sandvik CH440 Main Shaft Step — Part No. 452.0531-001

The main shaft step in a Sandvik CH440 cone crusher carries the full axial thrust load of the main shaft assembly during every crushing cycle. Positioned at the base of the main shaft inside the bottom shell, it acts as the primary bearing interface between the rotating shaft and the stationary frame. In a CH440 operating at rated feed capacity, the downward thrust force transmitted through this component can exceed 300 kN under peak crushing conditions. A step that fails to maintain dimensional stability and surface integrity under this load does not wear gradually — it triggers accelerated damage to the main shaft lower journal, the bottom shell bore, and the eccentric bushing assembly in a sequence that escalates repair scope with each additional operating hour the machine runs in a degraded condition.

Material and Mechanical Properties

This replacement main shaft step is cast from high-leaded tin bronze conforming to ASTM B22 Alloy C93700. The nominal composition is 79 to 81 percent copper, 9 to 11 percent tin, and 8 to 11 percent lead, with phosphorus held below 0.05 percent and iron below 0.15 percent. In the as-cast condition, Brinell hardness runs HB 55 to HB 70 and compressive yield strength is approximately 90 MPa. The dispersed lead phase in the C93700 microstructure serves as a boundary-phase solid lubricant at the shaft contact surface during startup conditions, before the pressurised oil supply from the CH440 lubrication circuit has established a full hydrodynamic film across the load-bearing face. This characteristic is critical in jaw and cone crusher parts that undergo frequent planned stops and restarts as part of normal quarry or mine production scheduling.

Oil Groove Geometry and Surface Specification

The upper load face is machined with a radial petal-pattern oil groove array designed to distribute pressurised lubricating oil across the full bearing surface and provide a continuous escape path for fine wear debris generated during boundary contact at startup. Oil groove depth is held at 1.5 to 2.0 mm with groove width of 4 to 6 mm, machined to a surface finish of Ra 3.2 to 6.3 μm on the groove walls. The load-bearing lands between grooves are precision-finished to Ra 0.8 to 1.6 μm to support stable hydrodynamic film formation under full operating load. The seating face on the underside of the step is ground flat to within 0.05 mm across the full component diameter, ensuring even load distribution against the CH440 bottom shell seat and eliminating the contact stress concentrations that cause edge-zone fatigue cracking in improperly seated thrust components.

Dimensional Compliance

Installation Notes

• Inspect the bottom shell seat and lower shaft journal before fitting. Any fretting marks or out-of-round deviation exceeding 0.15 mm on the shaft seat surface will generate uneven contact stress on the new step face and initiate surface fatigue within the first operating hours. Restore both mating surfaces to drawing specification before installation.
• Confirm oil supply flow rate before first startup. The CH440 lubrication system must deliver filtered oil to the bottom shell circuit at the Sandvik-specified flow rate before the main drive is energised. Dry startup, even momentarily, causes boundary contact temperatures that transfer bronze material to the shaft journal and score both surfaces permanently.
• Use ISO VG 220 or ISO VG 320 EP gear oil as specified in the Sandvik CH440 maintenance manual. Non-EP oil or incorrect viscosity grade reduces film thickness at operating temperature and directly shortens step service life.
• Monitor oil return temperature continuously. A rise of more than 10 °C above the established steady-state baseline at constant throughput is the earliest reliable indicator of deteriorating step condition in cone crusher parts assemblies of this type. Schedule inspection before audible symptoms develop.