The 3.4x5x8mm Black Compression Spring is a compact, high-resilience helical coil spring engineered for precise mechanical tensioning, shock absorption, and return-action mechanisms in small-scale assemblies. Manufactured from durable spring steel with a corrosion-resistant black oxide finish, this micro-compression spring provides consistent spring rates, high fatigue resistance, and reliable linear force in tight spaces, making it an essential hardware component for 3D printer hotends, extruder tensioners, RC models, and precision robotics.

Specification

• Product Type: Helical Micro-Compression Spring
• Inner Diameter (ID): 3.4mm
• Outer Diameter (OD): Approx. 4.8mm - 5.0mm
• Free Length (Uncompressed Height): 8.0mm
• Wire Diameter: Approx. 0.7mm - 0.8mm
• Material: High-Grade Carbon Spring Steel / Music Wire Alloy
• Surface Finish: Black Oxide / Black Electrophoretic Anti-Corrosion Coating
• End Configuration: Closed and Ground / Squared Ends (Ensures perpendicular seating and uniform load transfer)
• Load Type: Linear Axial Compression
• Fastener / Shaft Compatibility: Fits over standard M3 screws, guide pins, and 3.0mm - 3.2mm dowels; slides cleanly into 5.0mm - 5.5mm counterbores.

Features

• High Fatigue Resistance & Elastic Recovery: Formulated from tempered spring steel that resists permanent deformation and mechanical sagging even under continuous, repetitive compression cycles.
• Protective Black Surface Treatment: Coated with a wear-resistant black finish that provides protection against atmospheric oxidation, workshop oils, and moisture while maintaining a clean aesthetic.
• Squared and Stable Seating: Designed with closed coil ends to provide a flat, stable contact surface against washers, screw heads, or cavity bases, preventing bowing and uneven force distribution.
• Compact Form Factor: Engineered for tight spaces where controlled push-back, pre-loading, or damping force is required without adding excessive weight or volume.
• Consistent Linear Spring Rate: Delivers predictable, proportional resistance across its compression range, ensuring repeatable tensioning and mechanical reliability.

Common Applications

• 3D Printer Extruder Idler Tension: Providing reliable clamping pressure on drive gear idler arms to ensure slip-free filament feeding across direct-drive and Bowden extruders.
• Hotend & Toolhead Assemblies: Pre-loading auto-bed leveling sensor pins, heat break mountings, or micro-switch trigger mechanisms.
• RC Models & Robotics: Serving as compact suspension springs, push-rod return elements, servo-saver buffers, and gripper tensioners.
• Precision Electronics & Fixtures: Providing tactile return-force in push buttons, mechanical switches, testing jigs, and PCB alignment clamps.

Professional Installation and Maintenance Tips

• Do Not Exceed Solid Height: Avoid compressing the spring completely flat (solid height) for extended periods to prevent plastic deformation and premature loss of spring elasticity.
• Use a Center Guide Pin or Bore: To prevent lateral buckling during heavy compression, ensure the spring is supported either internally with an M3 screw/pin or externally within a matching 5.0mm bore.
• Apply Light Lubrication in High-Cycle Use: For mechanisms undergoing rapid, continuous cycling (such as robotic actuators or trigger links), apply a drop of light machine oil or PTFE lubricant to minimize friction wear.
• Ensure Perpendicular Mounting: Verify that the mounting surfaces on both ends are flat and parallel to maintain straight axial compression and prevent side-loading.