Understanding Hand Taps and Dies

Welcome back to the eighth installment of my threading series! In this article, we’ll explore the essential tools for manually cutting threads: hand taps and dies. We’ll discuss their functionality, types, and techniques, providing practical insights to enhance your threading skills.

?

The differences between a Hand Tap and Die

Before we get into the practical aspects, let's take a moment to differentiate between taps and dies. Taps are designed to create internal threads in a hole, allowing bolts to be securely fastened. Dies are designed to produce external threads on a rod or shaft. While both tools share the common goal of cutting threads, the key lies in choosing the right tool for a specific application.

?

Choosing the Right Tap or Die and Material Considerations

Selecting the right tap or die depends on the material you’re working with. For softer materials, carbon steel taps and dies are commonly used, while High-Speed Steel is preferred for harder materials like stainless steel. Carbide taps, known for their superior heat and wear resistance, are primarily used in high-production environments where they reduce cycle times. However, carbide taps are generally not recommended for hand use due to their brittleness, which can lead to breakage if not handled with care.

To cut effectively, taps and dies must be harder than the material they are working on. While the steel type and heat treatment processes ensure that taps and dies are sufficiently hard, this also makes them more brittle. Consequently, improper use can result in breakage, and removing a broken tap from a hole can be challenging.

?

Cutting Threads Using a Hand Tap

Ensuring the longevity of taps involves using the right tools and techniques. The tap wrench emerges as a primary tool, accompanied by a focus on proper technique to avoid breakage. Lubricating threads is essential to reduce friction and facilitate chip removal, a critical aspect of the tapping process. Techniques such as breaking up chips by reversing the tap's direction a quarter revolution and maintaining proper stress on the tap are emphasized for optimal results.

?

Types of Hand Taps

Hand taps come in different types: plug, taper, and bottoming.

• Plug Taps (also known as intermediate taps or second taps) are the most common and versatile, suitable for general-purpose applications. They feature a short chamfer that helps start threads straight and can complete threads almost to the bottom of a blind hole.
• Taper Taps, sometimes referred to as starter taps, start narrow and taper to their full width over several threads. They are ideal for initiating threads, making them easier to start, but they are not suitable for threading all the way to the bottom of a blind hole.
• Bottoming Taps, often called bottom taps or finishing taps, have no taper and are specifically designed to finish threads at the bottom of a blind hole. Since they cannot start threads effectively, they should be used after a taper or plug tap has been used to start the threading process.

?

Cutting Threads Using a Die

Dies specializes in creating external threads on metal rods. Proper preparation of the rod is critical to ensure you produce a good thread. Things like having a chamfer at the start of the threaded section of the rod, securing it in a strong vice, and using a generous amount of cutting fluid are essential steps in the die-threading process. Techniques such as breaking up chips and using a wire brush to clean up the threads are important factors.

?

Tap or Die Sizing

When using hand taps and dies, we can typically see two main thread series, which are the ISO METRIC, measured in millimeters, and ISO UN, measured in inches. A thread pitch gauge is recommended for accurate identification of which thread you are trying to replicate.

?

Final thoughts

Hand taps and dies are vital tools in the manufacturing process and indispensable in any workshop. This article has examined their functionality, various types, and essential techniques for manually cutting threads. With these insights, you now have a strong foundation to enhance your threading capabilities.

?

In the next article, I’ll explore "machine taps," which are essential for high-volume, consistent, and precise threading operations on CNC machines. Until then, keep threading and stay tuned for more insights into machining.