Thumb Screws M8 Hand Knob Bolts Plastic Five-Star Head Black Length 20-80mm

Measure the total grip length — the combined thickness of all materials the bolt must pass through — then add at least 10–15 mm for thread engagement in the nut or tapped hole. For example, a 12 mm panel fastened into a 15 mm tapped block needs a minimum of 27 mm of thread; the M8×30mm variant is the closest safe choice.

The carbon steel shank offers comparable tensile strength to a standard Grade 4.8 metric bolt for light-to-medium clamping loads. These thumb screws are designed for hand-tightened assemblies — jigs, guards, access panels — not for high-torque structural joints. If your application requires a specific proof load, contact us to confirm suitability.

The carbon steel shank has a standard black finish that provides limited corrosion resistance. For outdoor exposure or consistently humid environments (e.g., marine, food processing), consider applying a corrosion-inhibiting coating or contact us to confirm if a stainless variant is available. The plastic knob itself is unaffected by moisture.

Yes — the M8 × 1.25 mm metric coarse thread is the global standard for M8 fasteners and is compatible with the overwhelming majority of M8 tapped holes, weld nuts, T-slot nuts, and threaded inserts used in aluminium extrusion systems (e.g., 20-series, 30-series, 40-series profiles) and steel fabrications.

These are a popular choice for 3D printer bed levelling knobs, enclosure panel fasteners, and CNC machine guard bolts where the original hardware requires a tool to remove. Confirm that your existing fastener is M8 × 1.25 mm and select a length that matches your current bolt's grip length. The five-star profile provides good finger grip even with gloves.

For a single repair or prototype, the 1-piece pack is the most economical entry point. For a typical four-corner panel or jig with a spare, the 5-piece pack offers the best per-unit value. The 10-piece pack suits production runs, stocking a parts bin, or builds with multiple access panels. Per-unit cost decreases with larger pack quantities.

The exact knob outer diameter varies slightly by length variant. As a conservative estimate, five-star M8 knobs of this type typically measure 35–45 mm across the widest point of the star. If clearance is critical, please contact us to confirm the exact dimension for your chosen length before ordering.