Thread Pitch

Thread pitch is the distance from one thread crest to the next along the axis of a fastener. It describes how tightly the threads are spaced and is one of the key dimensions that determines whether a bolt or screw will properly mate with a nut or tapped hole. In metric fasteners, pitch is typically stated directly in millimeters (for example, M10 × 1.5 means a 1.5 mm pitch). In inch-series (Unified) fasteners, thread spacing is commonly expressed as threads per inch (TPI), where a higher TPI indicates a finer thread.

Thread pitch matters because it affects fit, strength, and performance in the application. Coarse threads (larger pitch or lower TPI) generally install faster, are more tolerant of dirty or damaged threads, and tend to hold well in softer materials. Fine threads (smaller pitch or higher TPI) offer more precise adjustment, often provide better resistance to loosening from vibration, and can deliver higher clamping force for a given torque, but they are typically more sensitive to cross-threading and damage. Matching the correct pitch is critical, since even fasteners with the same diameter will not assemble if their thread pitch differs.