Question: Some doubts regarding bolts and nuts?
Thread Content
1. How can coarse-threaded and fine-threaded nuts be distinguished? Under what conditions are they each applied? 2. Are all common bolts used in daily applications coarse-threaded? 3. Why aren’t types I and II, as well as coarse and fine threads, indicated in the bolt specifications? How can they be distinguished? 4. Is writing the pitch equivalent to specifying fine threads, in my personal opinion?
1. The codes for coarse and fine threads are the same; when the major diameter of the thread is identical, the pitch and profile height of a fine thread are smaller than those of a coarse thread. For specific details, refer to GB/T 193-2. Generally, coarse-threaded screws are used for connections, while fine-threaded screws are suitable for connecting thin-walled parts. For example, they are used in situations where pre-tension is required, as fine-threaded screws have a higher self-locking property than coarse-threaded screws, resulting in greater pre-tension. In applications where high precision is required, such as the threads on seals. The design is subject to restrictions, such as the requirement for a more compact structure. When designing transmission components for tooling, fine-threaded screws can be used as precision drive shafts when sealing is required. 3. Bolts must be specified in accordance with their standard requirements, as these standards provide classifications for them. 4. Coarse threads generally do not require the pitch to be indicated, while fine threads must have their pitch specified
Why are there no Type I or Type II nuts for sizes above M36? Are all those used above M36 fine-threaded?
It depends on the standard you want to use; for example, GB/T6175 covers only up to M36, while GB/T6170 goes up to M64. Each standard has its own maximum limit, and for larger sizes, you can design custom standards of your own
But is the 6170 a Type I nut, making it unsuitable for use in flammable and explosive environments?