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Differences Between Screws, Machine Screws, Studs, Lead Screws, and Bolts

May 24, 2024

Differences Between Screws, Machine Screws, Studs, Lead Screws, and Bolts

In mechanical design and manufacturing, threaded fasteners are essential components. They are used not only for joining and fastening but also for transmitting power and motion. This article will explain the differences between screws, machine screws, studs, lead screws, and bolts, referring to national standards for clarity.

1. Screws

Screws are externally threaded fasteners that can be inserted into pre-made holes by rotating. Screws typically do not require a nut and can self-tap into materials. Common types include wood screws and drywall screws. According to the GB/T 15856 standard, screws are characterized by their pointed ends which allow them to penetrate materials directly.

2. Machine Screws

Machine screws are similar to screws but are mainly used with nuts or driven into pre-tapped holes. They usually have smaller diameters and higher precision, widely used in various mechanical devices. According to the GB/T 70.1 standard, machine screws have different head and drive types to suit different applications.

3. Studs

Studs are fasteners with threads on both ends, used in applications requiring high-strength connections. One end of the stud is screwed into a component, and the other end is secured with a nut. According to the GB/T 901 standard, studs are commonly used in engine cylinder heads and other high-strength connection areas.

4. Lead Screws

Lead screws are typically used for power transmission or motion and are mechanical drive components. Lead screws have threads that can pair with nuts to achieve linear motion. They are common in machine tools and screw conveyors. According to the GB/T 17587 standard, lead screws require high precision in thread form and accuracy.

5. Bolts

Bolts are externally threaded fasteners that require a nut for use. Bolts are primarily used where a high clamping force is required. According to the GB/T 5782 standard, bolts typically have hex heads and flat ends, forming a secure connection with nuts. Common types of bolts include hex head bolts and anchor bolts.

National Standards Reference


Screws, machine screws, studs, lead screws, and bolts each have unique applications and characteristics. Understanding their differences and relevant standards is crucial for mechanical design and manufacturing.