4.0 x 20-40 Three-Step Blue-White Zinc T17 Semi-Countersunk Head Self-Tapping Screw

Product Overview
This product has a diameter of 4.0 mm and lengths from 20 to 40 mm. It is made of C1022 carbon steel with quenching and features a blue‑white zinc anti‑rust surface treatment. Combined with a semi‑countersunk Torx recess, a T17 cutting point, and a three‑step segmented coarse thread, it is a cost‑effective general‑purpose self‑tapping screw for indoor woodworking and wood‑steel composite fixing, available in multiple sizes to suit various panel assembly needs.

Product Applications
Whole‑House Customisation: Splicing and assembly of wardrobes, kitchen cabinets, display cabinets, and various wooden panels.
Decoration Projects: Fixing wood joist ceilings, partitions, door frames, skirting boards, and edge trims; can also be used in combination with thin light‑gauge steel.
Wood Product Processing: Batch assembly of wooden crates, pallets, and wooden shelving.
Note: Suitable for dry or mildly humid indoor environments only. Not recommended for outdoor use, coastal high‑salt spray areas, or steel plates thicker than 2.5 mm.