CNC threading, or numerically controlled threading, is a machining technique that involves creating threads on metal surfaces using specialized CNC machines. This process utilizes precise tools to create accurate and repeatable threads, which is crucial in industrial production.
Threading on a CNC lathe
A CNC lathe is one of the most commonly used types of machines for threading. The threading process on a CNC lathe involves machining the external surface of an element. The computer-controlled machine processes details with high precision, creating threads of a specified profile and diameter.
Threading on a CNC milling machine
A CNC milling machine is another device used in the threading process. Unlike a lathe, the CNC milling machine is used for threading holes. This mechanism consists of a rotating mill, which is numerically controlled, allowing for the creation of a thread of the desired shape and size.
What are threading parameters?
Threading parameters, such as diameter, direction, and thread angle, are set using the CNC machine control program. Other important parameters include thread depth, thread direction (right-hand or left-hand), and thread type (e.g., metric, inch). Precise setting of these parameters is crucial for the proper functioning of the finished element. Below is a detailed description of the key threading parameters:
- Thread diameter - This is one of the most important values in the threading process. The thread diameter is the distance between opposite points on the thread walls. We can distinguish the external diameter (maximum distance between the peaks of the thread) and the internal diameter (minimum distance between the valleys of the thread). This value depends on the type and size of the thread we want to create.
- Thread direction - The thread direction, also known as the helix, defines whether the thread is right-handed or left-handed. Right-handed threads tighten when turned in the direction of the clock hands, while left-handed threads tighten when turned counter to the direction of the clock hands. The choice of thread direction depends on the end use of the item.
- Thread angle - The thread angle is the angle measured between the symmetrical walls of the thread profile. Its value depends on the type of thread - for example, in a metric thread this angle is 60 degrees, while in an inch thread (UNC/UNF) it is 55 degrees.
- Thread depth - The thread depth is the distance between the peak and the valley of the thread. This is an important parameter that affects the strength and functionality of the thread.
- Thread type - The thread type determines its shape and profile. There are many different types of threads, including metric, inch, trapezoidal, or pipe threads. Each of them has its specific application and requires the use of the appropriate tool for its execution.
Threading on CNC machines
Threading on CNC machines is a technique that involves a numerically controlled process of creating both external and internal threads. Specialized tools such as taps and milling cutters are used for this purpose. The advantage of this technique is high precision and repeatability, which is extremely important in serial production.
Threading holes
Threading holes is one of the key applications of CNC threading. Thanks to precise numerical control, it is possible to create internal threads with specified parameters. This process is extremely important in the production of machine parts and devices, where the accuracy of the thread can affect the functioning of the entire system of mechanisms.
CNC metal threading
This process is widely used in the metal industry. Thanks to advanced CNC technology, it is possible to thread various types of metals, such as:
- steel,
- aluminum,
- copper,
- titanium.
This process allows for the creation of very precise and repeatable threads, which are crucial in many branches of industry.
What is thread rolling?
Thread rolling is an alternative method of threading that involves deforming the material using special rollers. This technique is often used where exceptional thread strength is required, such as in the automotive industry. Thread rolling can also be carried out on CNC (numerically controlled) machines, which ensures even greater precision and repeatability of the process.
How does the CNC threading process work?
The threading process on CNC machines begins with the selection of the appropriate tool, which is mounted in the machine's holder. For external threading, cutting tools such as turning knives are often used, while for internal threading, taps or mills are used. Then, using CNC software, the machine programmer sets all necessary parameters. These include, among others, the thread diameter, the number of threads per inch, the thread depth, the thread direction (right-hand or left-hand), and the thread type. After setting these parameters, the machine is ready to start the threading process. During the threading process, the cutting tool rotates at the appropriate speed and moves along the path programmed in the CNC software. As a result of this process, a thread with programmed parameters is created on the surface of the machined part.
In which products can CNC threading be applied?
CNC threading has many applications in various industries. Thanks to its precision and repeatability, it is perfect in situations where each element must meet strict standards. In the automotive industry, CNC threading is used to produce many components, such as:
- screws,
- nuts,
- shafts, and many more.
In the aviation sector, precise threads are crucial for the safety and reliability of aircraft. In heavy industry, such as wind turbine manufacturing or mining equipment, threads must be exceptionally durable, which can be achieved thanks to CNC threading technology.
Machine Taps and Characteristics of Holes
Machine taps are tools that are specifically designed for the threading process. They are very durable and long-lasting, which means they can be used for a long time without wearing out. The holes in which we make threads can be "through" or "blind". Through holes are those that go through the entire material, while blind holes are those that end within the material. Threading through holes is usually easier, as chips can escape from the other side of the hole. Sometimes taps are coated with a special material to increase their durability.
What are internal threads and how are they created?
Internal thread machining is performed using a single-edge threading tool instead of a conventional tap. When parts have internal holes requiring threading, it is necessary to remove the actual threads from the CAD model, leaving only the major diameter. Properly created software is able to identify the hole subject to threading, if:
- It fits within the diameters of the appropriate thread,
- It is aligned with one of the three main milling axes,
- It is orthogonal to the axis of rotation on the lathe.
It is also possible to thread internally on turned parts. Many of the techniques described can be applied to threading on a lathe using powered tools, although the available threads may be more limited than in milling. The range of UNC and UNF threads ranges from #4-40 to ½-20, and metric threads fluctuate around from M3 to M10. With the use of active fixtures, it is possible to make radial, axial, and central threads. This affects threading, as some threads are only available in the central position. During machining with an internal thread, the hole can be deeper than the threading tool's capabilities. In such a case, there are several options to consider, depending on specific requirements. We describe them below:
- Using a deeper tool - If longer tapping tools are available, they can be used for machining deeper holes. However, it should be noted that longer tools may be less stable and will increase the risk of cracking or damage.
- Manual processing - If the machine is unable to thread to the required depth, manual processing may be an alternative to this process. However, this means additional costs and time.
- Design change - In some cases, it is possible to design a part to reduce the thread depth without affecting its functionality.
- Use of thread cutting technology without chip evacuation - In the case of holes with large depths, thread cutting technology without chip evacuation, such as dry threading, may be an appropriate solution. This allows for the creation of threads at a great depth without the need to remove chips.
Each of the above options has its advantages and disadvantages, therefore the choice of the appropriate solution depends on the specific requirements of a given project and tool limitations. It is important to consider these factors when designing parts and planning the threading process.
What are external threads and how do they work?
The integration of lathes into technological processes has enabled us to expand our offer of external threading. We are able to offer various sizes of external threads, provided that your parts are compatible with the turning process. We use a custom threading tool, which is tailored to specific thread sizes, depths, and locations in the part geometry. The modern turning technique we use allows for the creation of external threads on the centerline of the part - just like numerically controlled tools, they allow for internal hole threading, as long as the same guidelines as in the milling process are followed. This is not limited to central holes only - threads can also be made on axial and radial holes.
How to create external threads?
Just like with internal threads, designing external threads for parts machined on lathes requires the removal of actual threads from the CAD model so that the software can identify them. Additionally, external threads should be modeled with milling in mind, not turning. External threads are less frequently designed on parts compared to internal threads, however, we are able to effectively execute them. External threads are created with half the diameter of the tool, after which the machined part is rotated by 180 degrees, and threads on the opposite side are made in the same way. For large, thicker external threads, this method works well. External threads of small sizes, such as 6-32, are harder to produce using a ball or flat mill, due to the fact that a larger radius would remain at the base of the thread when the pitch is too small. In such a case, it may be necessary to carry out the process through a thread machining tool to remove excess material.
The role of torque during the threading process
The torque applied to the spindle of a CNC machine is one of the most important aspects of the threading process. It is responsible for the force used to rotate the tap, allowing it to cut the material. It must be large enough for the tap to cut through the material and create a thread, but not so large as to damage the tool or the material. Moreover, excessive torque can lead to excessive tool wear and even breakage. On the other hand, too low torque can cause the tap to be unable to properly cut the material, which can lead to thread defects.
Torque regulation
In CNC machines, the torque can be regulated, which allows for precise adjustment to the requirements of a specific task. Adjusting the torque to the material and the size of the thread to be created is crucial for achieving optimal results. Monitoring and supervision are also extremely important.
torque during the threading process. Sudden jumps in torque can indicate problems, such as a jammed tap, which can lead to damage to the machine or tool. Many CNC machines have built-in monitoring systems that can automatically stop the entire process if the torque exceeds a safe range.
Summary
CNC threading is a process in which we create threads in holes, or patterns on the surface of the hole. When we do this on a machine, we use machine taps. During threading, it is important to carefully select cutting parameters, such as cutting speed and feed. Cutting speed is the speed at which the tap moves through the material, while feed is the distance the tap moves per one rotation. For example, if the cutting speed is 800, it means that the tap moves at a speed of 800 meters per minute. Torque is the force we need to apply to the spindle (the part of the machine that rotates the tap) to rotate at the appropriate speed. This is important because too much force can damage the tap or the material, and too little - can make the threading ineffective. To properly perform the threading process, you need to have the appropriate skills and knowledge. This includes the ability to properly select taps, set cutting parameters, and properly operate the machine. Without this, the threading process can be difficult and potentially dangerous, as well as lead to damage to the material or tools. Our company and qualified staff will help you navigate through this challenging process.