McKissick M-491G Derrick Hoist Block - 12 Ton - 5/8 in Wire Rope - 14 in Sheave - Roll Forged

Product Description

The McKissick M-491G Derrick Hoist Block is a heavy-duty hoisting block engineered for derrick and crane applications where reliable load handling, precision bearing performance, and sheave durability are critical to operational uptime. Rated for a 12-ton working load limit and compatible with wire rope cable up to 5/8 inch in diameter, this block is built for sustained use in oilfield, marine, offshore, and heavy construction derrick systems where consistent performance under repeated high-load cycles is required. The M-491G designation is part of McKissick's purpose-built derrick block line, designed to meet the demanding requirements of vertical hoisting in fixed and mobile derrick configurations.

The block features a sealed tapered roller bearing, providing superior load-carrying capacity, precise sheave alignment, and effective resistance to contamination from dirt, moisture, and field debris. The sealed design eliminates the need for frequent regreasing in the field, reducing maintenance intervals and extending service life in remote or offshore environments where regular servicing may not be practical. The 14-inch OD roll forged sheave delivers enhanced grain structure, greater surface hardness, and improved resistance to groove wear and deformation compared to cast sheaves — characteristics that are particularly valuable in high-cycle wire rope hoisting applications where sheave longevity directly affects rope service life and system reliability.

The M-491G is configured for applications where a slightly smaller sheave diameter and wire rope size than the M-491S variant are appropriate, offering a well-matched combination of capacity, sheave geometry, and bearing performance for 5/8-inch wire rope derrick hoisting systems. This block is suitable for use in derrick hoisting systems, crane blocks, and other fixed or mobile lifting configurations requiring a robust, low-maintenance hoisting block. Always confirm wire rope diameter compatibility, attachment hardware ratings, reeving configuration, and full system load ratings before placing the block into service.

Material:

Steel block body Roll forged sheave Sealed tapered roller bearing

Compatible With:

Wire rope cable up to 5/8 in diameter

Uses:

Derrick hoisting systems Crane and hoist block applications Oilfield and offshore lifting operations Heavy construction vertical hoisting Fixed and mobile derrick configurations

Key Features:

12 Ton working load limit 14 in OD roll forged sheave Accepts wire rope up to 5/8 in diameter Sealed tapered roller bearing for high load capacity and contamination resistance Maintenance-reduced sealed bearing design M-491G Derrick series construction