Guide to Metal Threading

Threading metal is an important metalworking technique that produces efficient fastening systems that are used in a wide range of industries and in the home.

What is the difference between threading and tapping? Metal threads can be either external or internal (male or female threads). Threading uses a die to create threads on the outside of a solid bar. Tapping makes threads inside a hole, using a tapping tool. What is the best metal for threading? A range of metals is used, but high-speed and carbon steels are particularly popular.

Read on to learn more about metal threading, metal threading tools, and some of the common applications of threaded metal.

What is metal threading? Threading metal creates helical grooves (either screws or nut-screws) on (or within) metal surfaces. This allows them to fasten to other items with similar threading. It is one of the most widespread metalworking practices. Although threads vary widely, there are some principles that apply to creating them engineers must always consider. They include:

• Whether the thread is internal or external. If machining is carried out on an internal surface the thread is known as a ‘female thread’. If the thread is carried out on an external surface it is known as a ‘male thread’.
• The profile of the thread. Threads should be designed with an ideal geometric profile in mind, although the thread as it is executed will vary from that a little.
• The pitch of the thread. This pitch is the distance between two consecutive ridges on the metal thread. The pitch is proportional to the height of the workpiece. Assuming there is just one continuous thread on the fastener, the pitch indicates how far the screw will travel with each turn.
• Screw direction. Engineers must consider the direction of the screw. Screws are said to be right-handed if they run clockwise to tighten, and left-handed if they run anti-clockwise. The vast majority of screws are right-handed.

What tool is used to thread metal? Threading tools come in a variety of types, including taps and dies. You’ll probably be wondering, ‘what is a tap and die set used for?’ Read on to find out more.

One extremely common way of creating threaded metal is using taps and dies, threading taps, die holders, and die nuts. Metal taps and dies rose to prominence in the 18th and 19th centuries in industries such as transport, textiles, and defence.

Just what are taps and dies used for? Taps create the female component of the fastener, such as a nut or socket, and a die is used to make the screw or bolt (male component). Taps and dies can also be used for rethreading existing threads, known as ‘thread cleaning’.

You may be wondering how to use a tap and die set, how to create a threaded hole in metal, and how to make threading on metal.

We’ve got you covered.

When using a tap, first, drill your hole. Using a tap / die drill chart helps choose the correct drill bit for the hole. Drill the hole, and then place the square of the tap in the tap holder. Tighten it up and place the tip of the tap in the hole. (The tap should be as close as possible to perpendicular to the hole.) Push down and turn the tap. The tap will begin to cut a thread into the side of the hole. Once you have made three complete turns, reverse the direction for three-quarters of a turn, which will expel the chip out of the hole.

Dies work in a similar manner but are used on cylinders and rods instead of a drilled hole. If you’re using a die, it should be the same nominal size as the cylinder. If you’re using taps and dies to create threads, employing cutting fluids can help make the process smoother and reduce tool wear.

Taps are often referred to as ‘threading taps’ and come in different shapes. It’s important to choose the right type of threading tap for your project. Threading tap types include plug taps, taper taps, spiral flute taps, spiral point taps, and bottoming taps. Bottoming taps are used to create threads in blind holes, while taper taps, as the name suggests, feature a taper along the tap.

Taper taps are usually used when starting a thread. Plug taps feature a short taper and bigger diameter than standard taper taps. Spiral flute taps are ideal for use on softer materials and feature a spiral flute, which helps to remove chips from the workpiece. Spiral point taps perform a similar function but are better for hard materials. They are distinctive because of their pointed end and spiral groove running along the length of the tool.

Die holders (also known as ‘die stocks’) are tubular parts for fitting and turning dies when cutting threads into rods, cylinders, or pipes. They are made from a range of heavy-duty materials for longevity and come in different sizes, with special handles to assist grip. Using a die stock helps ensure the die is in exactly the right position during threading. This helps create accurate threads.

Die nuts come into their own when sharpening threads that are blunt or have been otherwise damaged. Die nuts, sometimes also referred to as ‘thread chasers,’ look like a square or hexagonal nut. They are available in a range of sizes, types, and threads, and are manipulated with a spanner.

Screws are one of the most commonly machined and used components in the world. They are a widespread and vital method of creating fastenings in not only manufacturing and construction, but also domestically. Metal threading applications include threaded fasteners such as bolts and nuts, threaded seals for pipework, and screws for connecting materials including metal, fibreglass, and wood.

Although fasteners have been used in industry for a very long time, innovations in thread design and manufacturing continue. These are set to develop further with the advent of advanced materials and manufacturing techniques, which will enhance the performance and reliability of threads.

Want to get started threading metal? Explore RS’s range of threading tap and die sets now.