KITO
Blocks
Blocks—encompassing crane blocks, snatch blocks, hoisting blocks, and overhaul balls—are the load‑bearing housings that integrate sheaves, bearings, swivels, and shackle connections into a complete wire rope interface for overhead lifting. The block transfers the rope tension into the load, multiplies the mechanical advantage of the reeving system, and provides the swivel rotation necessary to prevent rope twisting as the load is lifted, slewed, and placed. Crosby 566 Hoisting Blocks feature galvanised assemblies with flame‑hardened roll‑forged sheaves, tapered roller bearings on stainless‑steel centre pins, permanently sealed swivel thrust bearings, and pressure lubrication fittings. Rated by maximum single‑line pull and proof‑tested at four times working load, they are supplied with ABS‑recognised load test certificates. Gunnebo Johnson manufactures a comprehensive range of crane blocks up to 150 tonnes capacity.
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Integrated Sheave‑to‑Shell Engineering
Block shells are designed as a matched system with their sheaves, eliminating the mismatches in groove alignment, bearing fit, and rim clearance that occur when blocks are assembled from unbranded components.
Permanently Sealed Swivel Thrust Bearing
The swivel assembly is factory‑sealed and lubricated for life, preventing the ingress of dirt and moisture that causes swivel seizure and the resultant rope‑twisting that can spin a suspended load uncontrollably.
Pressure Lubrication for Field Maintenance
Grease fittings on both the centre pin and swivel enable in‑situ re‑lubrication without disassembly, supporting the scheduled maintenance that extends bearing service life in high‑cycle crane applications.
Flame‑Hardened Roll‑Forged Sheaves
Sheaves 14″ and larger feature a hardened groove surface that resists the abrasive wear of loaded wire rope, maintaining the correct groove profile over thousands of lift cycles.
Proof‑Tested with ABS‑Recognised Certification
Every block is individually proof‑tested and supplied with an ABS‑recognised load test certificate, satisfying the documentation requirements for class‑society‑regulated lifting appliances.
5:1 Design Factor on Resultant Load
The block structure provides an ultimate strength of 5× the resultant load in multi‑part reeving systems, giving rigging engineers a calculable safety margin for complex lift planning.
Preventing Rope Jamming: The Critical Shell‑Sheave Interface
The gap between the sheave rim and the block shell is one of the most consequential dimensional tolerances in crane engineering. If the gap exceeds the wire rope diameter, a slack rope can jump the groove and wedge itself between the sheave and the shell, jamming the block and stopping the lift mid‑operation. Freeing a jammed rope often requires cutting the rope—sacrificing a multi‑thousand‑dollar wire rope—followed by block disassembly to extract the trapped section. Crosby 566 blocks prevent this failure by machining the sheave mortise close to the shell, maintaining a gap smaller than the rope diameter throughout the full 360° of sheave rotation.
Snatch Blocks vs. Hoisting Blocks: When to Use Each
Snatch blocks are designed for temporary rigging where the rope must be inserted and removed quickly without threading. They feature a side‑opening gate or removable cheek plate that allows the rope to be placed over the sheave mid‑rope rather than fed through from the end, making them essential for winching, pulling, and directional change applications. Hoisting blocks such as the Crosby 566 are permanently reeved into crane wire rope systems and are optimised for continuous high‑cycle lifting with sealed bearings, close‑fitting shells, and integrated swivels. Using a snatch block in a permanent hoisting application risks rope derailment, while using a hoisting block for one‑off winching adds unnecessary rigging complexity.