CN
EN
Complete Industrial Thread Classification & Application Guide
Release time：2026.08.17
Source：Dexin Metal
Views：3
Differences Between Metric, UNC, UNF & Special Custom Threads for Industrial Fasteners
Metric Thread (M Thread) – The Most Widely Used Standard
Metric thread is the international general standard for industrial fasteners, commonly known as M thread. It adopts millimeters as the unit of measurement and features uniform tooth pitch and stable versatility. Metric threads are divided into standard coarse threads and partial fine threads, suitable for most mechanical equipment, furniture, electronic products and general engineering assembly.
The biggest advantage of metric threads is strong compatibility, easy installation and convenient after-sales maintenance. Most conventional screws, nuts, stud bolts and furniture fasteners adopt metric thread standards. With moderate tooth depth and strong bite force, it is not easy to slip during daily assembly and disassembly, making it the mainstream thread type for mass production fasteners.
UNC Coarse Thread – American Standard Coarse Thread
UNC (Unified National Coarse) thread is the American standard coarse thread. Compared with fine threads, UNC has fewer threads per inch, larger tooth pitch and thicker tooth shape. Its core feature is quick assembly and strong anti-loosening performance in ordinary vibration environments.
UNC coarse threads have a stronger tolerance for assembly holes, not easy to jam during locking, and are more suitable for on-site rapid installation, construction machinery, automobile parts and general industrial equipment. Due to the thick thread structure, UNC threads are not easy to wear, and have better durability in frequently disassembled parts.
UNF Fine Thread – American Standard Fine Thread
UNF (Unified National Fine) thread is a fine-pitch American standard thread. It has more threads per inch, denser tooth arrangement and higher fitting precision. Fine threads have stronger tensile strength and better locking performance under high pressure and high vibration conditions.
Different from coarse threads, UNF fine threads can provide a more uniform pre-tightening force, effectively preventing loosening under long-term vibration, impact and high-load working conditions. It is widely used in precision machinery, automobile engines, aerospace accessories and high-pressure equipment connections. Fine threads require higher production precision and stricter thread tolerance control during manufacturing.
Special & Custom Non-Standard Threads
In addition to conventional standard threads, a lot of industrial equipment, home appliances, smart devices and customized machinery require non-standard special threads. This includes special pitch threads, partial fine and partial coarse mixed threads, special tooth angle threads, and asymmetric custom threads.
Custom threads are specially designed for special assembly space, anti-loosening requirements and equipment structural limitations. Such threads cannot be purchased from conventional markets and require professional mold opening, thread rolling and precision forming processes. Dexin Metal supports all kinds of non-standard thread customization, providing one-stop solutions for special fastener needs of global customers.
How to Choose the Right Thread Type?
For general assembly, furniture and conventional machinery, metric coarse thread is the most cost-effective and universal choice. For quick installation and general industrial equipment, UNC coarse thread is preferred. For high-precision, anti-vibration and high-load equipment, UNF fine thread can significantly improve connection stability. For special equipment and exclusive structural design, customized non-standard threads ensure perfect assembly matching.
Conclusion
Thread type is the core detail that determines fastener quality and assembly effect. Distinguishing metric, UNC, UNF and custom threads helps engineers and buyers avoid matching errors and improve project installation accuracy. Dexin Metal strictly controls thread precision for all standard and custom fasteners, supporting mass production and personalized thread customization to meet diverse industrial connection demands.
News recommendation
Standard & Custom Wrench Guide: L-Shaped, Z-Shaped and Special Custom Wrenches
2026-08-12
Structure, Manufacturing Process & Furniture Assembly Application
2026-08-10
Double End Stud Bolt: Classification, Production Process & Industrial Application Guide
2026-08-06
How Are High-Quality Industrial Nuts Manufactured? Complete Standard Production Process
2026-08-04
Screw Surface Treatment & Salt Spray Standard Guide｜Dongguan Dexin Metal Co., Ltd.
2026-07-31