Complete Guide to Machine Screws: Types, Sizes & Applications

Machine screws are threaded fasteners designed for use with pre-threaded holes or nuts. Unlike self-tapping screws, machine screws require a pre-tapped hole and are primarily used in metal-to-metal assembly applications. These screws feature uniform threading along their entire shaft and come with various head types including Phillips, Allen (socket head), slotted, and Torx drives. At ScrewBazar, we supply machine screws in sizes ranging from tiny M1.6 screws for electronics to robust M12 screws for heavy machinery.

Shop Machine Screws →

Allen screws feature a cylindrical head with hexagonal socket, driven by Allen keys (hex keys). They're the preferred choice for applications requiring high clamping force and are commonly used in machinery, automotive, robotics, and industrial equipment. Popular sizes include M3, M4, M5, M6, and M8, available in stainless steel SS304 and mild steel with zinc plating. Their advantages include high torque capacity, clean appearance, and space-efficient design. Allen screws pair perfectly with hex nuts or nyloc nuts for secure fastening.

Browse Allen Screws →

Phillips machine screws are the most common type used in consumer electronics and appliances. They feature pan head, flat head, or round head with a Phillips (cross-head) screwdriver drive. The cross-head design allows for better torque transfer and prevents cam-out. These screws are widely used in electronics, appliances, furniture, and HVAC systems. Available in M2 to M8 sizes, they offer easy installation, self-centering capability, and widely available tools. Often used with plain washers for better load distribution.

Torx machine screws offer superior performance with their star-shaped drive, providing the highest torque transfer with no cam-out and longer tool life. They're popular in modern electronics, automotive assembly, and security applications. Slotted machine screws, though traditional, remain popular in applications where aesthetics matter or for equipment restoration. They're common in vintage electronics and older machinery repair, offering simple design and universal tool compatibility.

Explore All Machine Screws →

Machine screws follow metric sizing (M series) in India. M3 and M4 are most commonly used in electronics, appliances, and general machinery assembly. Materials include stainless steel SS304 (for outdoor, marine, food processing, medical devices), mild steel zinc-plated (for indoor machinery, electronics, automotive), brass (for electrical applications, marine hardware, decorative fixtures), and nylon (for electronics to prevent shorts, chemical environments, weight-sensitive applications). Always pair with appropriate washers and nuts for optimal performance.

Machine screws are essential across multiple industries: electronics manufacturing uses M2-M3 sizes for motherboards and components; industrial machinery relies on M4-M8 for CNC machines and packaging equipment; automotive industry uses Torx screws for dashboard and engine components; HVAC systems use stainless steel or zinc-plated screws for panel assembly; and appliances use hundreds of Phillips pan head screws for assembly. We supply bulk quantities to manufacturers across Bangalore, Mumbai, Delhi NCR, Chennai, Pune, and Ahmedabad.

Selection requires careful consideration: determine thread size using a thread gauge (M3 for electronics, M4 for general, M5-M6 for machinery); calculate required length by adding material thickness + nut thickness + 2-3 threads; select head type based on needs (Allen for high torque, Phillips for general purpose, Torx for automotive, Slotted for decorative); choose material based on environment (SS304 for outdoor/marine, MS zinc-plated for indoor, Brass for electrical, Nylon for electronics); and consider temperature, moisture, chemicals, and vibration factors.