CAT 544-4649 Lower Front Head Bushing

CAT 544-4649 is a Caterpillar original equipment lower front cylinder head bushing (with flange positioning type), suitable for the lower front cylinder head hinge area of ​​the boom lifting cylinder and stick cylinder of Cat 320D2/323D2 excavators, 966M loaders, etc. It is used to reduce friction between the cylinder head and the pin, bear radial loads, and provide positioning and guidance. The following is professional structured information from Cat® Parts:

Core Technical Parameters (Professional Version)

Item Details
Basic Attributes
Model 544-4649, Type: Flange-backed steel-bronze cylinder head bushing, suitable for the lower front cylinder head of Cat front-end work cylinders, material: steel backing + tin bronze alloy (CuSn8P), flange outer diameter φ100 mm, inner diameter φ60 mm, bushing body outer diameter φ80 mm, body length 45 mm, flange thickness 8 mm, single weight approximately 1.2 kg, rated bearing pressure 250 MPa, operating temperature – Operating temperature 30℃ to +120℃, compatible with NLGI 2 lithium-based grease (with EP additive), IP65 corrosion resistance, with internal lubrication grooves (3 axial grooves + 1 circumferential groove) and 2 radial grease injection holes.

Key Dimensions: Inner diameter tolerance +0.012/-0.008 mm, outer diameter tolerance +0.020/-0.015 mm, length tolerance ±0.15 mm, inner hole surface roughness Ra≤0.4 μm, outer diameter Ra≤1.6 μm, flange end face runout ≤0.05 mm, coaxiality ≤0.03 mm, chamfer at both ends 1.5×45°, flange perpendicularity to body ≤0.03 mm.

Material and Manufacturing Process: Steel backing made of Q235 low carbon steel (2.0 mm thick), bronze layer thickness 3.0 mm (containing graphite self-lubricating particles, content 3-5%), integrally sintered. Rolled and formed, with precision boring and honing of the inner bore, milling of the flange face, bronze layer hardness HB 80-90, steel back tensile strength ≥450 MPa, bronze layer bonding strength ≥150 MPa, free from defects such as cracks and porosity.
Compatible with Cat 320D2/323D2/326D2 excavator boom lifting cylinder lower front cylinder head, 966M/972M loader bucket cylinder lower front cylinder head, D6K/D7E bulldozer bulldozer blade cylinder lower front cylinder head. Suitable for cylinder hinge parts with a pin diameter of φ60 mm, commonly used with 544-4650 sealing rings and 544-4651 pins.
Assembly fit: Interference fit with cylinder head bore (0.020-0.030 mm), clearance fit with pin (0.08-0.12 mm). After installation, the flange end face should fit snugly against the cylinder head (deviation ≤ 0.1 mm), and the grease injection hole should be aligned with the cylinder head lubrication channel.

Installation and Maintenance Points:

Before installation, clean the bushing, cylinder head hole, and pin, checking for deformation, cracks, or bronze layer peeling. Cool the bushing with liquid nitrogen (-196℃, 5-10 minutes) before pressing it into the cylinder head hole, or use a special pressing tool to cold press it into place. Do not force it by hammering.

After installation, check that the bushing rotates/oscillates freely without jamming. Perform a 20-minute no-load test run, monitoring the temperature to ≤ 80℃. Check every 1000 hours. If the inner bore wear is > 0.2 mm or abnormal noise or leakage occurs, immediately replace the bushing and its matching seal.

The initial grease injection volume should be 1/2 of the bushing lubrication groove volume. Replenish every 800 hours. In dusty/humid conditions, shorten the interval to 400 hours to ensure adequate lubrication.