CAT 4P-3937 Gas Pressure Regulator Bushing

CAT 4P-3937 is a straight-tube wear-resistant bushing commonly used in Caterpillar construction machinery. It is suitable for low-speed, medium-load hinge parts such as the boom pin of the 320D/323D excavator, the rocker arm hinge of the 950GC loader, and the blade pivot of the 140M grader. Its core function is to reduce friction between the pin and the mounting hole, provide positioning, and compensate for assembly clearance. The following is structured technical and application information:

Core Technical Parameters

Item Details
Basic Attributes
Model 4P-3937, straight cylindrical oil-groove-free bushing, suitable for hinge pins of 320D/323D excavator booms, 950GC loader rocker arms, 140M grader blades, etc., material is tin bronze (ZCuSn10Pb1, containing 10% tin and 1% lead), good self-lubricating properties, operating temperature -30℃ to +110℃, single weight approximately 0.58 kg, suitable for grease lubrication, rated radial static load ≥45 kN, operating speed ≤120 rpm, wear life ≥3500 hours, used for friction reduction and positioning in hinged parts, limiting axial movement of the pin.

Key Dimensions
Inner diameter 50.80 mm (2.0 in, tolerance H7, +0.025/0 mm), outer diameter 57.15 mm (2.25 in, tolerance H7, +0.025/0 mm), g6 (-0.012/-0.028 mm), total length 44.45 mm (1.75 in, tolerance ±0.12 mm), wall thickness 3.175 mm, chamfered ends C1.0 mm, inner hole roughness Ra≤1.6 μm, no oil groove or oil hole, compatible with standard pins and mounting holes.

Material and Process: Tin bronze ZCuSn10Pb1 → centrifugal casting → solution treatment (520℃ holding for 2h) → rough turning → finish turning → fine grinding → deburring → rust prevention. It has good friction reduction, wear resistance, and anti-galling ability, suitable for low-speed, medium-load, and frequent oscillation conditions.

Compatible Models: Cat 320D/323D/326D excavator stick/boom hinge point, 950GC/966K loader rocker arm/connecting rod pin, 140M/160M grader blade connecting pin, 420D… This component is used for friction protection and positioning at the hinge joint of the skid steer loader’s working device, extending the life of the pin and mounting hole.

Assembly Fit: Compatible with 50.80 mm diameter pins (tolerance f7, -0.020/-0.045 mm), and 57.15 mm diameter mounting holes (tolerance H7, +0.025/0 mm). Clearance fit: 0.010-0.030 mm. Press-fit installation; welding or heating deformation is prohibited. After press-fitting, the inner hole roundness should be ≤0.02 mm.

Installation and Maintenance Points: Before installation, clean the pin, mounting hole, and bushing. Check for scratches, porosity, and rust. Measure the inner diameter of the mounting hole and the outer diameter of the bushing, ensuring a clearance of 0.010-0.030 mm. The surface roughness of the hole, Ra, should be ≤1.6 μm.

Press the bushing vertically using a hydraulic press, with a pressing force ≤80 kN. Ensure the bushing end face fits snugly against the mounting hole step without misalignment. Do not directly strike the bushing end face with a hammer to prevent deformation.

Maintenance Recommendations: Check the fit clearance every 1200 hours. Replace immediately if the radial clearance is >0.25 mm or if loosening or abnormal noise is observed. Lubricate routinely with NLGI 2 lithium-based grease, replenishing the grease every 200 hours. Prevent impurities from entering the friction surface.