CNC threading, or numerically controlled threading, is a machining technique that uses specialized CNC machines to create threads on metal surfaces. The process uses precision tools to create precise and repeatable lines, which is crucial in industrial manufacturing.
Threading on a CNC lathe
The CNC lathe is one of the most commonly used types of threading machines. The process of threading on a CNC lathe involves machining the outside surface of a component. The machine, which is computer-controlled, machines the workpiece with high precision, creating threads of a specific profile and diameter.
Threading on a CNC milling machine
The CNC milling machine is another device used in the threading process. Unlike a lathe, a CNC milling machine is used for threading holes. The mechanism consists of a rotating cutter that is numerically controlled, which allows the thread to be made in the desired shape and size.
What are threading parameters?
Threading parameters, such as diameter, thread direction, and angle, is set using the CNC machine control program. Other important parameters are:
- Thread depth.
- Thread direction (clockwise or counterclockwise).
- Thread type (e.g., metric, inch).
Precise setting of these parameters is crucial to properly functioning the finished part. Below is a detailed description of the key threading parameters:
- Thread diameter - This is one of the most important values in the threading process. Thread diameter is the distance between opposite points on the thread walls. We can distinguish between the outer diameter (the maximum distance between the peaks of the threads) and the inner diameter (the minimum distance between the valleys of the threads). This value depends on the type and size of the thread we want to create.
- Thread direction - Thread direction, or torsion, defines whether a thread is right-handed or left-handed. Right-handed threads tighten when turned clockwise, while left-handed threads tighten when turned counterclockwise. The choice of thread direction depends on the end use of the component.
- 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 - Thread depth is the distance between the tip and the valley of the thread. It is an important parameter that affects the strength and functionality of the thread.
- Thread type - The thread type determines its shape and profile. Many types of threads exist, including metric, inch, trapezoidal, or pipe threads. Each has its specific application and requires an appropriate tool to produce it.
Threading on CNC machine tools
CNC machine tool threading is a technique that involves a numerically controlled process to create threads, both external and internal. Specialized tools are used for this, such as taps and mills. The advantage of this technique is high precision and repeatability, which is extremely important in mass production.
Hole threading is one of the key applications of CNC threading. It is possible to produce internal threads with specific parameters thanks to precise numerical control. This process is critical in producing machine and equipment components, where thread accuracy can affect the functioning of the entire mechanism system.
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:
This process makes it possible to produce precise and repeatable threads, which are crucial in many industries.
What is thread rolling?
Thread rolling is an alternative threading method involving special rollers deforming the material. 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 makes the process even more precise and repeatable.
How does the CNC threading process work?
The process of threading on CNC machines begins with selecting the appropriate tool attached to the machine's chuck. Cutting tools such as lathe knives are often used for external threading, while for internal threading, taps or cutters are used. Then, the machine programmer uses CNC software to set all the necessary parameters. These include thread diameter, number of threads per inch, thread depth, thread direction (clockwise or counterclockwise), and thread type. Once these parameters are set, the machine is ready to start the threading process. During the threading operation, the cutting tool rotates at the appropriate speed and moves along the path programmed in the CNC software. As a result, a thread with the programmed parameters is formed on the surface of the workpiece.
What products can CNC threading be used in?
CNC threading has many applications in various industries. Due to the precision and repeatability of the process, it is ideal in situations where each part must meet strict standards. In the automotive sector, CNC threading is used to manufacture many components, such as:
- shafts and many others.
Precision threading is crucial for aircraft safety and reliability in the aerospace sector. In heavy industry, such as the manufacture of wind turbines and mining equipment, threads need to be extremely strong, which is made possible by CNC threading technology.
Machine taps and hole characteristics
Machine taps are tools that are specifically designed for the threading process. They are very strong and durable, which means they can be used for long without wearing out. The holes in which we make threads can be "through holes" or "blind holes." Through holes are those that go all the way through the material, and non-through holes are those that end up inside the material. Threading through holes is usually easier because the chips can escape from the other side of the hole. Sometimes taps are coated with a unique material to increase their durability.
What are internal threads, and how are they formed?
Internal threads are machined using a single-edge threading tool instead of a conventional tapping. When parts have internal holes requiring tapping, removing the actual threads from the CAD model is necessary, leaving only the parent diameter. The adequately developed software can identify a hole to be tapped if:
- It falls within the diameters of the corresponding thread,
- It is aligned with one of the three principal milling axes,
- It is orthogonal to the axis of rotation in the lathe.
Internal threading on lathe workpieces is also possible. Many techniques described can be applied to threading on a lathe using live tools, although the available threads may be more limited than milling. The range of UNC and UNF threads is from #4-40 to ½-20, and metric threads oscillate in the neighborhood of M3 to M10. Radial, axial, and central threads can be produced with active tooling. This affects threading, as some threads are only available in the central position. When machining with internal threads, the hole may be deeper than the capabilities of the threading tool. In this case, there are several options to consider, depending on your specific requirements. We describe them below:
- Using a deeper tool - If longer threading tools are available, they can be used to machine deeper holes. However, it is worth noting that longer tools may be less stable and will increase the risk of breakage or damage.
- Manual machining - If a machine cannot thread to the required depth, manual machining may be an alternative to this process. However, this means additional cost and time.
- Redesign - In some cases, designing a part to reduce the thread depth without affecting its functionality is possible.
- Using no-tapping technology - For holes with large depths, no-tapping technology, such as dry tapping, can be a suitable solution. This allows threads to be created to great depths without the need for chip removal.
Each of the above options has advantages and disadvantages, so choosing the right solution depends on the specific requirements of the project and tooling constraints. It is essential to consider these factors when designing parts and planning the threading process.
What are external threads, and how do they work?
Integrating lathes into our processes has enabled us to increase our offerings for making external threads. We can offer different sizes of external threads, provided your parts are compatible with the turning process. We use a custom threading tool tailored to specific thread sizes, depths, and locations in the part geometry. The modern turning technique allows us to create external threads on the centerline of the part - just as numerically controlled tools allow us to thread internal holes, as long as the same guidelines are followed in the milling process. This is not limited to center holes - threads can also be made on axial and radial holes.
How to create external threads?
As with internal threads, designing external lines for parts machined on lathes requires removing the existing threads from the CAD model so that the software can identify them. In addition, external threads should be modeled with milling rather than turning in mind. External threads are less frequently designed on parts than internal threads, but we can effectively produce them. External threads are created with half the diameter of the tool, after which the machined part is rotated 180 degrees, and the threads on the opposite side are made the same way. For large, thicker external threads, this method works well. External threads of small sizes, such as 6-32, are more challenging to produce with a ball or flat cutter because a larger radius would remain at the base of the thread when the pitch is too small. In this case, running the process through a threading tool may be necessary to remove excess material.
The role of torque during the threading process
The torque applied to the CNC machine spindle is one of the most critical aspects of the threading process. It is responsible for the force to turn the threading machine, allowing it to cut the material. It must be large enough for the threader to cut through the material and form a thread but not so large that it damages the tool or the material. In addition, too much torque can lead to excessive wear on the tool or even break the tool. On the other hand, too little torque can cause the threader to be unable to cut the material properly, leading to a defective thread.
On CNC machines, torque can be adjusted, allowing it to be fine-tuned to the requirements of a particular job. Adapting the torque to the material and the thread size to be created is crucial for optimal results. Monitoring and supervising the torque during the threading process is also extremely important. Sudden torque spikes can indicate problems, such as a blocked threader, which can damage the machine or tool. Many CNC machines have built-in monitoring systems to stop the entire process if the torque exceeds the safe range.
CNC tapping is a process in which we create threads in holes or patterns on the surface of a hole. When we do it on a machine, we use machine taps. When threading, carefully selecting cutting parameters, such as cutting speed and feed rate, is essential. Cutting speed is the speed at which the threader moves through the material, while feed rate is the distance the threader moves per revolution. For example, if the cutting speed is 800, the threader moves at 800 meters per minute. Torque is the force we must apply to the spindle (the part of the machine that turns the thread cutter) to make it rotate at the right speed. This is important because too much force can damage the threader or the material, and too little force can make threading ineffective. You must have the right skills and knowledge to properly perform the threading process. This includes appropriately selecting threading dies, setting cutting parameters, and properly operating the machine. Without this, the threading process can be difficult and potentially dangerous and lead to damage to the material or tools. Our company and skilled staff can help you through this challenging process.