Cutting threads: Everything you need to know

Thread cutting is a widely practiced machining technique that enables the creation of threads. While it’s commonly used in industrial settings and by professional artisans, it’s equally accessible for hobbyists and beginners who are eager to explore this skill. If you’re curious about thread cutting, why not dive in? We’ll provide all the information you need to get started.

Why Mastering Thread Cutting is Beneficial

In today’s era of abundant hardware store options and readily available individual parts online, you might question the relevance of learning thread cutting. However, there are strong reasons why mastering this skill could prove valuable. Being able to cut threads gives you immense flexibility. You can fabricate components tailored to your requirements, avoiding waste and unnecessary costs. Furthermore, you can add threads to non-standard components that don’t fit typical dimensions if you learn how to cut threads effectively. Basic knowledge of thread cutting is also crucial if you ever need to repair a damaged thread.

Internal and External Threads: Two Sides of the Same Coin

Threads come in two main types: internal threads (such as those found inside nuts) and external threads (like those on bolts). The underlying principle remains the same—sharp cutting edges remove material to form the grooves. However, the practical aspects of cutting these threads vary significantly.

Cutting Internal Threads

To cut internal threads, you’ll require one or more tap sets. Before starting, though, it’s essential to prepare the core hole using a spiral drill bit of the precise size. Only the necessary amount of material should be removed during thread cutting. If the hole is too small, the tool can jam or break; if it’s too large, the thread won’t form properly. You can calculate the correct core hole dimensions using a formula or refer to a table. Chamfering the edge of the hole before cutting the thread is also advisable.

Cutting External Threads

For external threads on bolts or screws, you’ll need a die. Some preparation is needed before beginning the cutting process. First, choose the appropriate bolt and determine its pre-work diameter, which functions similarly to the core hole diameter when cutting internal threads. Guidance tables are available for this purpose. Afterward, chamfer the bolt before cutting the thread. Position the die vertically, apply slight pressure, and proceed with the cutting.

To Hand or Machine? That Is the Question

When cutting threads, you have the choice between doing it manually or using a machine. Both approaches have their pros and cons. Cutting threads by hand offers great flexibility and can be done anywhere without relying on electricity. It also avoids the need for costly equipment. On the flip side, using a stationary drilling machine saves considerable time, especially for high-volume thread cutting. Machines reduce human error, increasing the likelihood of achieving accurate results.

Cutting Threads by Hand

For hand-cutting internal threads, a multi-part hand thread tap set is required. These usually consist of three tools for coarse threads and two for fine threads. This division helps minimize effort. Each tool performs only part of the task, relying solely on muscle power. Alongside the taps, you’ll need an operating tool like a tap wrench or ratchet to guide the tap.

Hand-cutting external threads is also possible. For this, you’ll need a thread cutting die along with a die holder. Without mechanical assistance, ensuring the die remains straight during cutting is critical. A die guide can help maintain accuracy.

Machine-Assisted Thread Cutting

If you decide to use a machine for thread cutting, you’ll require a machine tap. Unlike hand tapping, a machine tap can complete the entire thread in one operation. Ensure your machine is suitable for thread cutting and preferably equipped with a thread cutting chuck. An automatic feed enhances the success of machine-assisted thread cutting. Avoid using machine taps in hand drills or cordless screwdrivers, as they pose a high risk of not starting straight, potentially leading to tool damage. Additionally, coolant is essential when cutting threads with a machine.

When cutting external threads on bolts or screws, the tool remains the same as in the manual approach. A regular die can still be used. To secure it in your stationary machine, you’ll need a die holder compatible with this setup.

Whether by hand or machine, external or internal threads – everything you need for thread cutting is available in various forms in our BAER online shop. As a trusted screw tap manufacturer, we offer a wide range of products including screw taps, thread cutting dies for diverse applications, twist drill bits, countersinks, and much more. Check out our selection today!