M3 M4 6#-32 Aluminum Knurled Thumb Screws w/without Spring Shock Absorber Bolts

Match the thread size to your existing threaded hole or insert. M3 and M4 are metric sizes used widely in European and Asian electronics and maker hardware. UNC 6#-32 is an imperial size common in North American electronics enclosures and rack-mount equipment. If you are unsure, measure the inner diameter of your threaded hole: M3 ≈ 3 mm, M4 ≈ 4 mm, 6#-32 ≈ 3.5 mm (0.138 in).

Choose the spring variant when your assembly is subject to vibration — for example, motor mounts, fan enclosures, vehicle-mounted electronics, or any panel that experiences repeated mechanical shock. The integrated compression spring maintains contact pressure between the head and the mating surface, reducing the tendency for the fastener to back out. For static, non-vibrating applications, the standard without-spring version is sufficient and slightly more compact.

These fasteners are designed for panel retention and access cover applications — not for load-bearing structural joints. Aluminum alloy provides adequate clamping force for securing enclosure panels, 3D printer covers, and similar light-duty assemblies. For applications requiring high clamping torque or structural integrity, stainless steel or steel thumb screws would be more appropriate.

Anodizing converts the outer layer of aluminum into aluminum oxide, which is harder than bare aluminum and provides moderate resistance to surface abrasion and mild corrosion from humidity and light chemical exposure. The anodized layer is not impervious to strong acids, alkalis, or salt spray over extended periods. For outdoor or marine environments, consider whether additional protection is needed.

Yes. M3 and M4 are the most common thread sizes in 3D printer frames, electronics enclosures, and maker hardware. The knurled head allows tool-free panel removal for filament changes, maintenance, or wiring access. The color options also allow color-coding of different access panels for quick identification.

The engaged thread length should be at least 1.5× the thread diameter for aluminum-to-aluminum joints (e.g., at least 4.5 mm for M3, 6 mm for M4). For threaded inserts in plastic or wood, follow the insert manufacturer's recommended engagement depth. If your application requires a specific shank length, contact us to confirm before ordering.

The color difference is purely cosmetic. All color variants use the same aluminum alloy base material and the same anodizing process; only the dye used in the anodizing bath differs. Mechanical properties, thread dimensions, and corrosion resistance are identical across all color options.