Cutting threads: Everything you need to know

Thread cutting is a widely used machining process that helps create threads. Although it's often employed on an industrial scale and by professional artisans, it’s also accessible for hobbyists and beginners eager to explore this skill. If you're curious about mastering thread cutting, now might be the perfect time to dive in. We’ll provide all the essential information to get you started.

Why Learning Thread Cutting Matters

With the abundance of hardware stores and easy access to individual parts online, you might question the relevance of learning thread cutting. However, there are strong motivations to invest time in this skill. By mastering thread cutting, you gain immense flexibility. You can craft components tailored to your specific requirements without unnecessary costs or waste. Additionally, you can modify unconventional parts that fall outside standard dimensions. Basic knowledge of thread cutting also proves invaluable when repairing damaged threads.

Internal and External Threads: Two Sides of the Same Coin

Threads come in two main types: internal and external. Commonly referred to as nut threads and screw threads, respectively, both share the same fundamental concept. Sharp cutting edges remove material to form thread grooves. Yet, the practicalities of cutting these threads vary significantly between internal and external versions.

Cutting Internal Threads

To cut internal threads, you’ll need a tap set, which usually consists of multiple tools for different thread types. Before starting, you must prepare the receiving core hole using a precisely sized spiral drill bit. Removing just enough material ensures proper thread formation. A hole that’s too small risks jamming or breaking the tool, while an oversized hole results in incomplete threading. You can determine the correct core hole dimensions using formulas or reference tables. Chamfering the hole’s edge before cutting also enhances precision.

Cutting External Threads

For external threads, such as those on bolts or screws, a die is used. Preparation is key here too. Start by selecting the appropriate bolt and determining its pre-work diameter, which functions similarly to the core hole diameter for internal threads. Reference tables can guide you in this step. Chamfering the bolt before threading is essential. Position the die vertically, apply gentle pressure, and begin cutting.

Hand vs. Machine Thread Cutting

Cutting threads can be done either manually or mechanically, each method offering distinct benefits. Manual thread cutting provides unmatched flexibility and requires no specialized equipment. This makes it ideal for situations where access to electricity is limited. However, using a stationary drilling machine significantly reduces cutting time, especially for high-volume projects. Machines also reduce human error, increasing the likelihood of achieving accurate results.

Manual Thread Cutting Techniques

For internal threads, you’ll need a multi-component hand thread tap set. These sets typically include tools for coarse and fine threads, dividing the work to reduce physical strain. Each tool handles a portion of the cutting, relying solely on human effort. Alongside the taps, you’ll require an operating tool like a tap wrench or ratchet to guide the process.

External thread cutting follows a similar approach. You’ll need a die and a die holder to keep it steady. Without mechanical assistance, maintaining the die’s alignment becomes critical. A die guide can help maintain straightness during cutting.

Machine-Assisted Thread Cutting

When opting for machine-based thread cutting, a machine tap is necessary. Unlike manual methods, machine taps allow you to complete the entire thread in one go. Ensure your machine is compatible with thread cutting and ideally equipped with a thread cutting chuck. An automated feed further improves the efficiency of this method. Avoid using machine taps in handheld drills or cordless screwdrivers—they’re prone to misalignment, leading to potential tool damage. Adequate coolant supply is also crucial during machine-assisted thread cutting.

When cutting external threads on bolts or screws, the tools remain the same as in manual setups. A regular die works effectively, but securing it in your stationary machine requires a compatible die holder.

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