Screws: types, sizes and drives

In short: Screws differ in thread, head, drive and material. Wood screws, machine screws and chipboard screws are not interchangeable.

In more detail: The size is given as diameter times length, e.g. 4 × 40 mm.

In detail

• Wood screws: Coarse thread with a point; pre-drilling prevents splitting.
• Chipboard screws: For furniture, with partial or full thread.
• Machine screws (metric): M4, M6, M8 etc., need a nut or threaded hole.
• Heads: Countersunk (flush), pan head, hex.
• Drives: Slotted, cross (PH, PZ), Torx, hex socket (Allen).
• Material: Zinc-plated, stainless steel (A2/A4 for outdoors), hardened steel.
• Matching bit: Choose the right drive and size, otherwise the head is stripped.
• Loosening stuck screws: Penetrating oil, heat, impact driver (werkzeug-grundausstattung-fuer-zuhause).