Knurled Thumb Screws M1.6–M5 Steel Hand-Tighten Knob Bolts

Match the thread diameter to your tapped hole or nut — M2 fits a 2mm threaded hole, M3 fits 3mm, and so on. For length, measure the total material thickness you need to clamp, then add 1–2 thread pitches for engagement. For example, clamping 4mm of material with an M3 screw typically calls for a 6–8mm length (≈1/4" to 5/16"). When in doubt, go slightly longer — you can always add a washer to reduce effective grip length.

These thumb screws are generally made from carbon steel with a surface treatment for corrosion resistance. The black finish variants typically use an oxide or coating process, while silver variants are generally left with a natural or zinc-plated finish. Contact us to confirm the exact alloy and treatment for your order.

These screws are generally suitable for light indoor use and protected outdoor applications. For prolonged exposure to moisture, rain, or salt air, we recommend applying a light coat of anti-corrosion spray or choosing stainless steel alternatives. Contact us if you need corrosion-rated options.

All sizes listed (M1.6, M2, M2.5, M3, M4, M5) use standard ISO metric coarse threads. They are not compatible with UNC/UNF imperial threaded holes. Always verify your application uses metric threading before ordering.

Anilox knurling features a cross-hatch (diamond) pattern that generally provides more grip surface area, making it easier to tighten by hand even with slightly oily or gloved hands. Straight Grain knurling has parallel vertical lines, offering a cleaner aesthetic that is popular in electronics enclosures and camera equipment. Both patterns are functional — choose based on your grip preference and visual requirements.

Thumb screws are designed for hand-tightening applications where tool-free adjustment is needed, not for high-torque structural joints. Typical hand-applied torque is generally in the range of 0.1–0.5 Nm depending on size, which is sufficient for panel fastening, equipment covers, and light fixtures. For load-bearing or vibration-prone assemblies, consider using a locking nut or thread-locking compound.

Yes — each size is available in packs of 1, 3, 5, 10, 25, 50, and 100 pieces. The per-unit price decreases as pack quantity increases, making bulk packs a cost-effective choice for production runs, repair kits, or stocking your workshop.