Ensure the correct rake angle on the screw tap

Thread cutting is often seen as a complex process, and many people find it challenging to achieve consistent results. The fear of broken taps and poor thread quality is real—but there's a way to improve your success rate. One key factor that often gets overlooked is the geometry of the screw tap. Understanding this can help you avoid common mistakes and make your threading work much smoother.

Today, we're diving into one of the most critical aspects of tap geometry: the rake angle, also known as the cutting angle. This angle plays a major role in how chips are formed during the cutting process, which ultimately affects the overall success of the thread cutting operation. In this article, we’ll explain what the rake angle is, why it matters, and how choosing the right one can make all the difference.

What Exactly Is the Rake Angle?

Before we get into the details, let’s start with the basics. The rake angle is an essential feature of any cutting tool, including screw taps. It refers to the angle between the chip surface and the tool reference plane, which is defined by the axis of rotation and the cutting point. This angle has a direct impact on how efficiently the material is removed during the cutting process.

Where Exactly Is the Rake Angle Located?

To better understand the concept, imagine looking at a screw tap from above, focusing on the middle of the thread. Now, draw a line from the center of the tap to the tip of one of the cutting edges. The angle between this line and the chip surface is the rake angle. It determines how the chip is formed and how easily it can be removed from the cut.

The Rake Angle Plays a Key Role in Chip Evacuation

One of the main functions of the rake angle is to influence chip formation and evacuation. A properly designed rake angle helps ensure that chips are formed consistently and removed effectively. If the angle is too small, chips can become large and difficult to remove, leading to clogging or damage. On the other hand, a larger rake angle allows for more efficient chip removal but may make the cutting edge more fragile.

How Does the Rake Angle Affect Cutting Performance?

The rake angle directly impacts the cutting force required during the threading process. A larger rake angle reduces the force needed, making the operation smoother and less stressful on both the tool and the machine. Conversely, a smaller rake angle increases the cutting force and friction, which can lead to faster tool wear and lower surface quality. Finding the right balance is crucial for optimal performance.

What Are the Advantages and Disadvantages of Different Rake Angles?

There’s no one-size-fits-all when it comes to the rake angle. A larger rake angle offers better chip control and reduced cutting force, but it can also make the cutting edge more prone to chipping. A smaller rake angle, while more durable, requires more force and can lead to increased heat and wear. Choosing the right angle depends on the material being cut and the specific application.

What Rake Angle Should You Use?

The ideal rake angle varies depending on the material you’re working with. Softer materials like aluminum can handle a larger rake angle (up to 18°), while harder or brittle materials like brass require a smaller angle (around 6°). Manufacturers like BAER design their taps with these considerations in mind, ensuring that each tap is optimized for specific materials and applications.

If you're unsure about the correct rake angle for your job, always check the manufacturer's specifications. And if necessary, the rake angle can even be adjusted through grinding. However, it's always best to start with a tap that's already suited to your material and task.

Don’t Confuse Rake Angle with Other Important Angles

It’s easy to mix up terms like rake angle, side rake angle, and helix angle. The side rake angle, for example, is often referred to as the spiral angle because it relates to the helical flute design of the tap. Meanwhile, the wedge angle and relief angle work together with the rake angle to form the complete cutting geometry. These angles must all be considered when selecting the right tap for the job.

Ready to take your thread cutting to the next level? Explore high-quality screw taps with precise cutting geometry in the BAER online store today. Choose the right tool for your project and enjoy better results every time!