Bolts in inches is “Unified National Coarse” (UNC) and “Unified National Fine” (UNF) for fine threads. These thread standards are commonly used in the United States and other countries that follow the imperial system of measurements.
The main term for bolts in metric is “ISO metric thread.” This thread standard is used in countries that follow the metric system of measurements, including most of Europe and many other regions worldwide.
It’s important to note that there are other thread standards as well, but UNC, UNF, and ISO metric threads are the most widely used and recognized for bolts in their respective measurement systems.
Bolt and Nut Thread Standards / National Coarse (NC)Threads per Inch
| Diameter | TPI (Threads per Inch) |
|---|---|
| #0-80 | 80 |
| #2-56 | 56 |
| #4-40 | 40 |
| #5-32 | 32 |
| #5-40 | 40 |
| #6-32 | 32 |
| #8-32 | 32 |
| 3/16″ | 24 |
| 1/4″ | 20 |
| 5/16″ | 18 |
| 3/8″ | 16 |
| 7/16″ | 14 |
| 1/2″ | 13 |
| 9/16″ | 12 |
| 5/8″ | 11 |
| 3/4″ | 10 |
| 7/8″ | 9 |
| 1″ | 8 |
| 1-1/8″ | 7 |
| 1-1/4″ | 7 |
| 1-3/8″ | 6 |
| 1-1/2″ | 6 |
| 1-5/8″ | 5 |
| 1-3/4″ | 5 |
| 1-7/8″ | 4.5 |
| 2″ | 4.5 |
| 2-1/4″ | 4 |
| 2-1/2″ | 4 |
| 2-3/4″ | 4 |
| 3″ | 4 |
| 3-1/4″ | 4 |
| 3-1/2″ | 4 |
| 3-3/4″ | 4 |
| 4″ | 4 |
Bolt and Nut Thread Standards / ISO metric thread in Pitch
| Diameter (mm) | Pitch (mm) |
|---|---|
| 1.6mm | 0.35 |
| 2mm | 0.4 |
| 2.5mm | 0.45 |
| 3mm | 0.5 |
| 4mm | 0.7 |
| 5mm | 0.8 |
| 6mm | 1 |
| 8mm | 1.25 |
| 10mm | 1.5 |
| 12mm | 1.75 |
| 14mm | 2 |
| 16mm | 2 |
| 18mm | 2.5 |
| 20mm | 2.5 |
| 22mm | 2.5 |
| 24mm | 3 |
| 27mm | 3 |
| 30mm | 3.5 |
| 33mm | 3.5 |
| 36mm | 4 |
| 40mm | 4 |
| 42mm | 4.5 |
| 45mm | 4.5 |
| 48mm | 5 |
| 52mm | 5 |
| 56mm | 5.5 |
There are several types of standards for threading of bolts and nuts. Here are some common types:
National Coarse (NC) and National Fine (NF) Standards: These are thread standards commonly used in the United States. NC threads have a wider pitch (fewer threads per inch) compared to NF threads, which have a finer pitch (more threads per inch).
Unified Thread Standard (UTS): The UTS is a standard that combines both the NC and NF threads into a single thread series. It is widely used in North America and is designated by the symbol “UN” followed by the thread size.
Metric Thread Standards: These standards are used in countries that primarily follow the metric system. They specify thread dimensions using millimeters (mm) instead of inches. The most commonly used metric thread standards include ISO metric threads and the British Standard Fine (BSF) and British Standard Whitworth (BSW) threads.
American National Standards Institute (ANSI): ANSI develops and promotes various standards, including those related to threading. ANSI standards cover a wide range of threads, including Unified and Metric threads.
International Organization for Standardization (ISO): ISO is an international standard-setting body that develops and publishes standards for various industries, including thread standards. ISO metric threads are widely used worldwide.
ISO metric thread refers to a standardized thread form for metric fasteners, as defined by the International Organization for Standardization (ISO). It is a widely accepted and used thread standard for metric bolts, nuts, and other threaded components.
ISO metric threads have a symmetric V-shaped profile with a 60-degree thread angle. The pitch is the distance between adjacent thread crests, and it is expressed in millimeters (mm). The thread pitch and diameter are specified together to define the thread size.
ISO metric threads are designed to provide a reliable and interchangeable connection between threaded components. They ensure compatibility and facilitate easy assembly and disassembly of fasteners.
The ISO metric thread standard covers a wide range of thread sizes and classes, providing options for various applications and requirements. It is widely used in industries worldwide that adopt the metric system of measurement.
DIN (Deutsches Institut für Normung) is the German Institute for Standardization. DIN standards cover various aspects, including threading of bolts and nuts. DIN threading standards are widely used in Germany and many other countries.
Some common DIN standards for threading of bolts and nuts include:
DIN 13: This standard covers ISO metric screw threads. It specifies the thread dimensions, tolerances, and designation system for metric threads.
DIN 931 and DIN 933: These standards specify partially threaded hexagon head bolts (DIN 931) and fully threaded hexagon head bolts (DIN 933) with metric threads. They provide details regarding thread sizes, lengths, and other dimensional requirements.
DIN 934: This standard covers hexagon nuts with metric threads. It specifies the dimensions, tolerances, and marking requirements for these nuts.
DIN 976: This standard pertains to metric stud bolts. It provides specifications for externally threaded rods with metric threads.
DIN 1587: This standard covers hexagon domed cap nuts with metric threads. It specifies the dimensions, tolerances, and marking requirements for these nuts.
These are just a few examples of DIN standards related to threading of bolts and nuts. DIN standards are widely recognized and used globally, particularly in Europe. It’s important to refer to the specific DIN standard applicable to your requirements to ensure proper thread selection and dimensional compatibility.
Bolt and Nut Standard used in Philippines
In the Philippines, the most common types of threads used for bolts and nuts are a combination of metric and Unified National Coarse (UNC) threads.
Metric threads, following the ISO metric thread standard, are commonly used for various applications in the Philippines. These threads are specified in millimeters (mm) and have a coarse pitch. Metric threads are widely used in machinery, automotive, construction, and other industries.
Unified National Coarse (UNC) threads are also prevalent in the Philippines, especially for certain applications such as structural bolts and fasteners. UNC threads follow the imperial system of measurement and have a coarse pitch.
It’s important to note that the specific thread type used in the Philippines can vary depending on the industry, application, and preferences of manufacturers and suppliers. It’s recommended to consult local industry standards, supplier catalogs, or engineering references for the precise thread types commonly used in the Philippines for specific applications.
Difference between Coarse and Fine Thread
The main difference between coarse and fine threads lies in their pitch, which is the distance between adjacent thread crests. Here are the key distinctions between coarse and fine threads:
1. Pitch: Coarse threads have a larger pitch (fewer threads per inch or millimeter) compared to fine threads. This means the distance between thread crests is greater in coarse threads.
2. Strength: Coarse threads are generally stronger than fine threads due to their larger cross-sectional area. The larger thread profile of coarse threads provides more material for load distribution and increased resistance to stripping or shearing.
3. Applications: Coarse threads are commonly used in applications where strength and quick assembly are important, such as structural connections or applications involving higher loads or forces. Fine threads, on the other hand, are often used in applications that require a higher level of precision, finer adjustments, or where vibration resistance is necessary.
4. Thread engagement: Coarse threads typically have more thread engagement compared to fine threads. This means that there is a greater number of thread turns engaged between the bolt and the nut, providing a more secure and reliable connection.
It’s important to select the appropriate thread type (coarse or fine) based on the specific application requirements, including the intended load, material compatibility, assembly speed, and desired level of precision.
Differences of Caps Screw (NC) vs Caps Screw (NF)
Caps screws, also known as machine screws, come in various thread standards, including NC (National Coarse) and NF (National Fine). Here’s a comparison between NC caps screws and NF caps screws:
NC Caps Screws:
- NC stands for National Coarse, which refers to the thread standard for the caps screws.
- NC threads have a larger pitch (fewer threads per inch) compared to NF threads, resulting in a coarser thread pattern.
- NC caps screws are commonly used in applications that require high strength and resistance to heavy loads or vibrations.
- They are suitable for general-purpose fastening, especially in applications where quick assembly or disassembly is required.
- NC caps screws are often used in machinery, equipment, and structural applications.
NF Caps Screws:
- NF stands for National Fine, which refers to the thread standard for the caps screws.
- NF threads have a smaller pitch (more threads per inch) compared to NC threads, resulting in a finer thread pattern.
- NF caps screws are used in applications that require increased thread engagement and finer adjustments.
- They are commonly used in applications that require a tighter fit, such as precision instruments, electronics, and delicate assemblies.
- NF caps screws provide better resistance against loosening and finer positional adjustment due to their finer threads.