M3 303 Stainless Steel Straight Knurled Thumb Screws — 6 to 20mm, 7 Lengths

Measure the depth of the threaded hole or the thickness of the material you need to fasten, then add any required thread engagement depth. Choose a length that provides at least full thread engagement without bottoming out. Available lengths are 6mm (≈0.24"), 8mm (≈0.31"), 10mm (≈0.39"), 12mm (≈0.47"), 14mm (≈0.55"), 16mm (≈0.63"), and 20mm (≈0.79"). When in doubt, a slightly longer screw is generally preferable to one that is too short.

303 stainless steel is a free-machining austenitic stainless steel with generally good tensile strength for M3-scale fasteners. It is stronger than aluminum and brass thumb screws of the same size, and provides better corrosion resistance than carbon steel. For M3 hand-tighten applications such as instrument panels, optical equipment, and electronics enclosures, 303 stainless steel typically provides sufficient strength. It is not intended for high-torque structural applications.

Yes. 303 stainless steel has good corrosion resistance due to its chromium content and generally performs well in humid, damp, and mildly corrosive environments. It is suitable for light outdoor use. For prolonged salt-spray or highly corrosive chemical environments, 316 stainless steel is typically recommended instead.

Yes. These use standard M3×0.5 metric coarse thread (ISO metric standard), compatible with any M3 nut, heat-set insert, or tapped hole following the ISO metric standard. Thread diameter is 3mm (≈0.118").

A straight knurled thumb screw has a cylindrical body with a straight (vertical) knurl pattern running along its length. This provides a secure finger grip along the full body of the screw, making it easy to apply consistent torque. Flat knurled thumb screws have a disc-shaped head with a low profile, while stepped knurled thumb screws have a tiered handle. The straight knurled style is commonly used in precision instruments, optical equipment, and scientific apparatus where a compact, grippy fastener is needed.

No. The straight knurled body is designed for finger-tight installation and removal without any tools. The knurl pattern provides enough grip for typical M3 hand-tighten torque. For applications requiring additional torque, a wrench or pliers can generally be used on the knurled body with care to avoid surface damage.

303 stainless steel offers a combination of corrosion resistance, strength, and machinability that aluminum and brass do not fully match. Aluminum is lighter but softer and more prone to thread stripping under repeated use. Brass has good corrosion resistance but lower tensile strength than stainless steel. 303 stainless steel is generally the preferred choice for applications where durability, repeated installation/removal cycles, and moderate corrosion resistance are all required.