Machine Screw

A machine screw is a headed fastener with a uniform machine thread for use with a tapped hole or nut. It is commonly used to assemble enclosures, instruments, electrical devices, appliances, and light machinery. The screw's uniform thread engages with a matching internal thread in a tapped hole or with a nut, allowing for secure clamping of components. When specifying a machine screw, buyers should consider head form, drive type, thread and pitch, length, property class, material, finish, and mating thread tolerance. These parameters must be selected based on the specific application requirements, including load, environment, and assembly method. Safety and load values cannot be inferred from appearance or nominal size; they must be obtained from the relevant product standard, approval documentation, engineering drawing, or test report. The request for quotation (RFQ) should also specify quantity, packaging, inspection, and traceability requirements to ensure the supplied parts meet the intended use. For reference, ISO 7045:2011 covers cross-recessed pan-head machine screws with nominal sizes typically ranging from M1.6 to M10, in materials such as steel, stainless steel, and brass by application. However, these values are indicative and must be confirmed against the exact product standard, drawing, approval, and manufacturer evidence. Always verify model-specific values and standards with the legal manufacturer or supplier before procurement.

The mating machine threads convert tightening torque into axial preload, which clamps the assembled parts together. When the screw is turned, the helical thread engages with the internal thread, and the applied torque creates tension along the screw's axis. This axial force presses the head against the top surface and the threaded portion against the internal thread, generating friction that holds the joint securely. The amount of preload depends on the torque applied, thread pitch, and friction coefficients. Proper tightening control is essential to achieve the desired clamp force without overstressing the screw or damaging the threads.