The Ultimate Guide to 4-40 Screws: Specifications, Types, and Applications
Screws are essential components in various mechanical applications, and among them, the #4-40 screw stands out due to its unique specifications and versatility. This guide aims to provide an in-depth understanding of the #4-40 screw, covering everything from its specifications to its applications. By the end, you’ll have a comprehensive grasp of this vital fastener.
| Type | Diameter (mm) | Threads per Inch (TPI) | Common Applications |
|---|---|---|---|
| #4-40 Screw | 2.695 – 2.827 | 40 | Electronics, mechanical assemblies, small devices |
| PEEK Socket Head Cap Screw | 2.695 – 2.827 | 40 | High-heat applications, medical devices |
| Stainless Steel #4-40 Screw | 2.695 – 2.827 | 40 | Corrosive environments, outdoor applications |
| Zinc-Plated #4-40 Screw | 2.695 – 2.827 | 40 | General-purpose use, indoor applications |
Understanding the 4-40 Thread Specification
The #4-40 screw is classified as a machine screw and features a thread that combines a diameter of #4 (approximately 2.695 mm to 2.827 mm) with 40 threads per inch (TPI). This combination is ideal for applications where a compact size is necessary while still providing high torque capabilities. The coarse threads make it easier to engage with materials, ensuring a secure fit.
Types of 4-40 Screws
1. Standard Machine Screws
Standard #4-40 screws are primarily made from stainless steel or zinc-plated steel. These materials offer excellent corrosion resistance and strength, making them suitable for various mechanical applications.
2. Socket Head Cap Screws
These screws feature a hexagonal socket in the head, allowing for better torque application. They are commonly used in assemblies where space is limited, and a lower profile is necessary. PEEK (Polyether Ether Ketone) variants are available for high-heat applications.
3. Specialty Screws
Some manufacturers, like www.extreme-bolt.com, offer specialty screws designed for specific industries, such as medical devices or aerospace applications. These screws often have unique coatings or materials to meet stringent industry standards.
Applications of 4-40 Screws
1. Electronics
Due to their small size and high torque capabilities, #4-40 screws are widely used in electronics for assembling devices such as circuit boards and enclosures. Their low head profile helps maintain a compact design.
2. Mechanical Assemblies
In mechanical applications, #4-40 screws provide reliable fastening for components like gears and housings. Their ability to withstand high torque makes them ideal for assemblies that experience vibration.
3. Medical Devices
Specialty variants, such as PEEK socket head cap screws, are used in medical devices due to their biocompatibility and resistance to sterilization processes.
Technical Features of 4-40 Screws
| Feature | Description |
|---|---|
| Thread Size | 40 TPI |
| Head Diameter | 0.219 inches |
| Head Height | 0.080 inches |
| Material Options | Stainless steel, zinc-plated, PEEK |
| Length Options | Ranges from 3/16″ to 2″ |
| Drive Type | Phillips pan head, hex socket |
Conclusion
The #4-40 screw is an indispensable component in numerous applications across various industries. Its specifications, such as diameter and threads per inch, cater to a variety of needs, from electronics to mechanical assemblies. With different materials available, including stainless steel and PEEK, these screws provide both strength and versatility. Understanding the nuances of #4-40 screws will aid in selecting the right fastener for your specific requirements.
FAQ
What is a #4-40 screw?
A #4-40 screw is a machine screw with a diameter of approximately 2.695 mm to 2.827 mm and 40 threads per inch. It is commonly used in applications requiring compact fastening solutions.
What materials are #4-40 screws made from?
These screws are typically made from stainless steel, zinc-plated steel, or specialty materials like PEEK for high-temperature applications.
What are the common applications for #4-40 screws?
4-40 screws are widely used in electronics, mechanical assemblies, and medical devices due to their strength and compact size.
How do I determine the length of a #4-40 screw?
4-40 screws are available in various lengths ranging from 3/16″ to 2″. The length should be chosen based on the specific application and material thickness.
What is the advantage of using a Phillips pan head?
The Phillips pan head design offers a wider surface area for better torque application and minimizes the risk of stripping or camout during installation.
Are #4-40 screws suitable for outdoor use?
Yes, stainless steel and zinc-plated variants offer corrosion resistance, making them suitable for outdoor applications.
What is the difference between coarse and fine threads?
Coarse threads, such as the 4-40, engage more easily with materials, while fine threads provide more holding power in softer materials.
Can #4-40 screws be used in high-torque applications?
Yes, their design allows them to withstand high torque, making them suitable for such applications.
Where can I purchase #4-40 screws?
4-40 screws are available from various suppliers, including www.mouser.com, www.mscdirect.com, and www.grainger.com.
What is the significance of TPI in screw specifications?
Threads per inch (TPI) indicate the density of threads along the screw’s shaft. Higher TPI provides finer adjustments, while lower TPI offers easier engagement in materials.