Hand Basket,Plastic Colorful Basket,Stores Shopping Baske,Colorful Plastic Basket Suzhou Malltek Supply China Co.,Ltd. , https://www.oktrolley.comWhere Exactly Is the Flank Angle Located?
How Does the Flank Angle Affect Performance?
Common Flank Angles You Should Know
Flank Angles in Pointed Threads
Flank Angles in Movement Threads
Special Cases and Historical Variations
Every thread profile is made up of a detailed set of precisely measured dimensions and angles, many of which might not be immediately obvious. While you don’t need to memorize all of them to cut quality threads, understanding a few key features can make a big difference in your work. Manufacturers take care of the complex calculations, ensuring that the final thread will fit as intended. However, there are some essential elements you should know—especially when it comes to selecting the right tap for your project. One such element is the flank angle.
The flank angle plays a crucial role in defining the shape of the thread. Although it may not be as well-known as other thread characteristics, its importance becomes clear when working with foreign standards or movement threads. In these cases, getting the flank angle right is critical. To help you stay informed, we’ve put together everything you need to know about flank angles and how they affect your projects.
To understand the flank angle, let’s start with the basics. Imagine looking at a thread from the side—this is called the profile view. If you were to slice through a screw or tap, you’d see the edges of the cut surface forming a jagged pattern, like a mountain range. The two sloping sides of each "mountain" are known as the flanks, and the angle between them is the flank angle.
This concept works well for standard pointed threads, but what about other types, like trapezoidal or round threads? Even in these cases, the flank angle still exists. If the flanks don't naturally meet, we can imagine extending them until they form a point. The angle between those imaginary lines is the flank angle. This helps ensure consistency across different thread designs.
The flank angle has a direct impact on friction and self-locking properties of a thread. In a screw connection, this means it influences how easily the fastener can be tightened or loosened. The smaller the flank angle, the smoother the thread, which reduces friction and makes it easier to move. On the other hand, a larger flank angle increases resistance, which is useful for applications where tightness is important, like in fastening threads. For motion threads, a smaller angle is preferred to allow for more efficient movement without excessive resistance.
Flank angles are standardized and are determined by years of engineering experience. As a result, only a few common values are used today. However, even small differences can cause incompatibility between threads. It's always wise to check the specific angle you're working with before proceeding.
Most pointed or fastening threads use a 60° flank angle. This includes metric threads, both coarse and fine, as well as American UNC, UNF, and UNEF threads. However, if you're dealing with British imperial threads, things are a bit different. BSW and BSF threads have a 55° flank angle, and the same goes for British pipe threads, especially the Whitworth G thread, which is commonly used in Germany.
Movement threads, such as those used in lead screws or linear actuators, typically have much smaller flank angles. The most common is around 30°, found in metric trapezoidal (Tr) and round (Rd) threads. The metric saw thread (S) has a slightly steeper angle at 33°. In contrast, the ACME thread used in the U.S. has a 29° flank angle, making it slightly different from its metric counterpart.
While most modern threads follow standard flank angles, there are exceptions. Some saw threads feature two different angles—one for the load-bearing flank and one for the non-load-bearing side. These are often used in specialized applications where unidirectional force is required. For example, metric saw threads might have a combination like 30° + 3°.
Historically, some thread designs had extreme flank angles. For instance, the steel armor pipe thread had an unusually large 80° angle. There were even older rectangular threads with a 0° flank angle, which were essentially right-angled. These were early predecessors to trapezoidal threads but were eventually replaced due to their difficulty in manufacturing and tendency to wear out quickly.
No matter what type of thread you're working with, we have the right tools for the job. Explore our collection at the BAER online store and feel free to reach out with any questions. We’re here to help you find the perfect tap or die for your project.