M3 M4 M5 M6 M8 M10 Knurled Thumb Screws 304 Stainless Steel Hand Grip Knob Bolts

Measure the total thickness of the material the screw must pass through, then add the engagement depth of your nut or threaded insert (typically 1–1.5× the thread diameter). For example, a 2 mm aluminum panel with an M4 T-nut requires at least 2 mm + 4–6 mm = 6–8 mm of thread length, so the 8 mm or 10 mm variant is appropriate. When in doubt, choose the next length up — excess thread beyond the nut does not affect function.

304 stainless steel has a tensile strength of approximately 515 MPa, which is adequate for panel retention, enclosure access doors, and light structural joints in aluminum extrusion frames. These screws are not intended for high-torque or high-vibration structural applications where a hex-head bolt with a torque wrench would be specified. For PC cases, 3D-printer enclosures, and similar maker applications, they are more than sufficient.

304 stainless steel contains approximately 18% chromium and 8% nickel, which forms a passive oxide layer that resists rust in most indoor and light outdoor environments. It is not fully immune to corrosion in chloride-rich environments (e.g., coastal salt air or chemical exposure). For typical workshop, office, or home-lab use, surface corrosion is not a concern under normal conditions.

The black oxide finish provides a dark, low-reflectance surface that blends naturally into black PC cases, dark enclosures, and stealth builds. The red anodized finish offers a high-contrast color that makes quick-release panels visually distinct — useful for color-coded maintenance access points or builds where you want specific fasteners to stand out. Both finishes are cosmetic; the underlying 304 stainless steel properties are identical.

Most ATX and mATX PC cases use M3 or M6 thumbscrew threads for side panels and expansion slot covers. The M3 × 5 mm or M3 × 8 mm variants are typically correct for side-panel retention, while M6 variants suit expansion slot screws on some cases. Check your case manual or measure the existing screw thread with a thread gauge to confirm before ordering.

Yes. Standard 2020, 3030, and 4040 aluminum extrusion profiles use M3, M4, M5, and M6 T-nuts respectively. Select the matching thread diameter and a length that provides at least 1× the thread diameter of engagement into the T-nut. These knurled thumb screws are a practical choice for access panels, hinged doors, and removable covers on extrusion-based enclosures and 3D-printer frames.

The 1-piece option is ideal for targeted replacements or when you need a single size to complete a build. The 5-piece option offers a lower per-unit cost and is practical when outfitting a full panel (typically 4–6 screws per side panel) or when you want spares on hand for future builds. Both options are available for every size and color combination.