Caterpillar S128

The Cat S128 is a mechanical scrap shear attachment for hydraulic excavators, not a self-powered machine. It carries no engine, ECM, or dedicated hydraulic circuit; the host excavator's own bucket cylinder drives the jaw through an extended linkage that multiplies cutting force at the throat and primary blade center. Stick-mounted, it fits Cat 330B carriers on a 3.3 to 3.9 m (10'10" to 12'10") stick and Cat 345B carriers on a 3.4 to 4.8 m (11'2" to 15'9") stick, matched to excavators in the 25,000 to 40,000 kg (55,000 to 88,000 lb) operating-weight class. Weight including the mounting bracket is 2400 kg (5,290 lb); jaw opening runs 400 to 500 mm (15.7 to 19.7 in) depending on carrier size, with a 570 mm (22.4 in) jaw depth. It shares its G125/G140 welded stick-mounting plate with Cat's mechanical grapples and pulverizers in the same weight class, and it shares its ADY serial-number range with its smaller sibling, the S115. Caterpillar cataloged it for automobile bodies, cable, small-diameter pipe, structural I-beams up to roughly 250 mm (10 in) high, and solid round or square stock, with a cycle time under 8 seconds on a 330B.

Caterpillar sold the S128 alongside the smaller S115 as a low-cost alternative to hydro-mechanical shears: skipping the dedicated shear cylinder, housing, and hydraulic installation kit kept purchase cost down, at the expense of matching a true hydraulic shear's cutting force. Cat later moved its scrap and demolition shear range to dedicated hydraulic designs that run their own cylinder instead of borrowing bucket-cylinder flow, and no direct model-for-model successor to the S128 is documented. In the used and parts market today, the S128 turns up on 330B- and 345B-era carriers still working scrap yards and demolition sites. Its appeal is low acquisition cost and mechanical simplicity with nothing electronic to fail, but because it is an out-of-production design, buyers should check remaining life on jaw pins, bushings, and blades before purchase and confirm rebuild-kit availability with a dealer rather than assume parts are stocked.

Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.