For anyone working with metal fabrication, plumbing, automotive repair or various other trades, knowing how to properly cut threads is an essential skill. Threading allows you to join pipes, rods and other components together in a precise, secure and removable fashion. While it may seem difficult at first, with the right tools and some practice, cutting clean, tight-fitting threads becomes second nature.

In this beginner's guide to threading, we'll cover everything you need to know to start mastering this useful technique. We'll discuss the different types of threads, the tools required, tips for getting optimal thread quality, and some common applications where threading comes into play.

Understanding thread types

Before you start chasing threads onto shafts and pipes, it's important to understand the different types of threads and their sizing conventions. The two main categories are:

Unified Threads: Used widely across many industries. Available in Unified Coarse (UN) and Unified Fine (UNF) pitches. Measured by threads per inch (e.g., 1/4-20 has 20 threads per inch)

Metric Threads: The standard in most countries outside of the US. Come in coarse and fine pitches. Measured by thread pitch in mm (e.g., M6 x 1.0)

Within those categories, threads also come in different series, such as UNC, UNF, UNRC, UNRF, M, MJ, and more. Each series has a specific shape, pitch, and application based on the strength and load characteristics needed.

Getting threads cut right

The secret to achieving high-quality threads is using the proper tools - and using them correctly. For most threading jobs, you'll rely on three main types of cutting tools:

Taps: Used to cut internal (female) threads into a predrilled hole

Dies: Used to cut external (male) threads onto a rod or pipe

Pipe taps: Pipe taps are specialized taps designed to chase threads onto the interior of pipes. Available in NPT and NPTF pipe thread styles.

When cutting threads with any of these tools, the key factors are:

• Cutting speed - Going too fast can tear and deform threads
• Feed rate - The feed rate must match the thread pitch being cut
• Lubrication - Using sufficient tapping fluid or thread-cutting oil is critical
• Chip clearing - Periodically backing out the tap/die to clear chips helps prevent galling
• Material - Choose the right HSS, cobalt, titanium, or other tap material for the base metal

Following manufacturers' specs for each tap or die, while developing a feel for the cutting process, are keys to getting threads cut cleanly and accurately.

A basic overview of threading tools

Let's take a closer look at the threading tools you'll use:

Taps - These are the most common threading tools, and they are used for cutting internal threads into holes. They are available in hand tap and machine tap styles in inch and metric sizes. Higher-quality taps are made from better steel and have specialized surface treatments and coatings.

Dies - For cutting external threads, dies are saw-toothed circular tools that clamp over a round bar or pipe and are guided by a die head. Dies come in handheld versions and semi-automatic styles.

Die Heads - These guide the die over the work to cut threads consistently. Adjustable and self-opening dies aid in proper die alignment and make changing out dies easier.

While you need several components to cut pipe threads or any threads properly, the tap is the primary workhorse that does the thread-cutting. Having high quality taps made from premium tool steel will last for many threading jobs.

On to applications

Now that you're familiar with threading concepts and tools let's discuss some common applications:

Plumbing/pipefitting - Creating watertight joints in pipes and fittings is one of the most frequent uses of threads.

Mechanical - Cutting threads in plates, rods, and fixtures enables the the assembling of precision parts and fastening devices together.

Automotive - Repairing spark plug threads, radiator fittings, and dozens of other automotive repairs requires chasing or cutting new threads.

The list goes on and on. Mastering different threading tools and techniques allows you to create solid, leak-proof, and removable connections on pipes, equipment, appliances, vehicles - anything with threaded components.

Conclusion

Like any skill, cutting threads takes time and practice to develop consistency. However, with a strong understanding of threads, quality threading tools, and proper technique, you can produce perfectly formed threads in a variety of materials for many different applications.

Don't get discouraged by dull, deformed, or sloppy threads at first - as you learn to control the cutting speed, feed rate, alignment, and other factors, your threading will become smoother, stronger, and more precise.