Threading is a common process in many factories. This processing generally belongs to finishing processing, and thread processing generally belongs to the last process. This is why it is important to understand tapping. One wrong move and the entire room could be abandoned, and no one wants that. Three common methods for tapping internal holes are tapping, countersinking and extrusion.
It can be difficult to consider using a squeeze faucet if you are unfamiliar with it or have never worked with a squeeze faucet in the past. Most people think that cutting taps should be used when drilling, but extrusion taps are a processing method that uses the principle of plastic deformation of metal to process internal threads, rather than cutting them.
Although the cutting tap method tends to be the most popular, extrusion taps offer significant advantages, depending on the application.
The biggest difference between extrusion taps is chip-free processing. When tapping, chips face the biggest challenge, especially processing deep holes.
Since no chips are generated, this type of extrusion tap tends to offer greater safety and productivity. It also tends to be more precise, ensuring exact dimensions.
The strength of the thread structure after extrusion tap processing is better, however, this also has some limitations, such as requiring more spindle power. While it can be used in most industries, the food, medical and aerospace sectors are exceptions.
When extruding, the tap compresses the material, creating a rabbit ear-like shape that includes gaps rather than a flat surface. This poses a problem for some industries because contaminants and particles can build up in the gaps.
The lifespan of extrusion taps is often 3 times (or more) that of other methods. For targeted materials, extrusion taps may be more suitable, but the editor is not sure factory bosses think so. There is a small initial cost, but the extended life of the faucet justifies the cost in many cases.
1
About threaded holes
When working with extrusion taps, the size of the pre-drilled hole (threading hole) is extremely important to the overall accuracy of the thread. Many operators unfamiliar with form taps may refer to standard or traditional tap sizes, but form taps have their own requirements. The technical instruction pages of many sample faucet brands specify the size requirements for the bottom hole.
Smaller diameters are less recommended with extrusion taps and therefore require tighter tolerances. If the drilled hole is too large or not precise enough, the material of the machined part will not be sufficiently extruded. On the other hand, if the hole is too small, the resistance will be great when the extrusion tap is involved in the work, possibly causing the tool to break.
Each extrusion tap size has a corresponding drill bit size, which is often larger than standard cutting tap sizes. For extrusion taps, you drill the oversized diameter so that it is slightly larger than the finished size.
During the extrusion process, you need to control two dimensions at the same time, the small diameter and the medium diameter, which is different from the cutting tap processing method, where the small diameter is drilled to the final size before tapping . The size of the hole is determined before the tap enters the hole. When the tap is ground, the small diameter constitutes the clearance, so there is no contact with the small diameter.
Without efficient and gentle material removal, it becomes very difficult to control dimensions and produce acceptable threads.
It is recommended to use a good hole processing tool (preferably a brand tap), measure the size of the bottom hole over time, and keep checking during the whole process, especially if there are many holes.
You need to ensure that the first and last holes are the same diameter so that the stability of the tool is improved. The editor also recommends here to check the holes and threads after the first form. Doing one first and checking it immediately can avoid a lot of downtime.
2
Material
The type and hardness of the material plays an important role in extrusion efficiency. If the material is too brittle or hard, the extrusion process will be impossible.
Aluminum, stainless steel, carbon steel, some alloys, and virtually any material up to 40HRC will work well with this method. Some tap brands will also have heat resistant superalloy options, especially the extrusion taps tested on 718, this works great.
The workpiece material must have a certain elongation (typically > 7%) to be able to produce the thread profile. Materials that are not very ductile, such as cast iron, must be machined using cutting taps.
Titanium can also pose a challenge because it has very low thermal conductivity, meaning it doesn’t absorb heat very well and the heat generated by faucet extrusion is difficult to dissipate. But for steel and aluminum, it is one of the strongest and most precise ways to extrude a tap.
Cutting taps can be problematic for small diameter threading applications in difficult-to-machine materials because the chips tend to be very hard and difficult to eject, leading to tap breakage. It’s not a question of molding.
Another advantage of a press-on tap is that it is not subject to shear forces, so when it comes into contact with the material it compresses the root of the thread profile and you get thread sides very smooth, thus improving the structural strength of the thread.
In addition, coating technology also plays an important role in the performance of forming taps. The material of the workpiece will determine the coating required for the faucet. Due to the chemical interaction between the coating and the material composition, they must match correctly. For example, if I use a tap coated with titanium nitride in 6061 aluminum alloy, the titanium nitride will chemically react with the metal and begin to interact with the metal. Press the combination. This will produce very poor results and reduced tool life. So the materials you use in aluminum are very different from those you use, for example, in stainless steel.
3
Machine tool factors
Torque specifications for thread milling and tapping are lower due to the cutting action. However, with extrusion taps (larger sizes), the torque required to remove material is much higher. This means that shops may need to consider larger, more powerful machine tools. One mistake many shops make is underestimating the power needed to drive the extrusion tap.
Compared to cutting taps, extrusion taps require approximately twice as much torque, and as tap sizes become larger, extrusion taps are no longer necessary. When considering large taps (>M20) or above, the use of extrusion taps tends to decrease as it requires a machine tool capable of producing high torque to operate effectively.
This method is ideal for high-volume CNC machining and achieves repeatable and consistent threads.
It is also important to have a good stiffness setting. The machine tool must be powerful, it must have stable clamping of the tool holder, and the workpiece must be strong. The recommended speed will be much faster than traditional cutting taps.
As the tap does not produce chips, the lighting inside the machine can be turned off. Because there are no chips, you can maintain good consistency in automated production and predict the effect of thread processing in advance. If you choose a good quality tap, you can have a prior understanding of the lifespan after several uses. Helps products enter automated processes and allows them to be smoothly introduced into shop floor production.
4
lubricant
During the threading process, heat is transferred to the workpiece, the tool and the chips; however, without the chips, heat enters the tool and material at a higher rate, which can cause problems. This is why coolant and lubricants are so important. Additionally, some extrusion taps are designed with unique geometries that help reduce cutting forces and therefore heat generation.
External cooling can be effective for this method because most extrusion taps have oil grooves on the exterior surface so that the cutting fluid can lubricate or cool the tap.
Extrusion taps require coolant or pure oil with higher lubricating properties. This is a high friction process because it pushes the material into a shape rather than shearing it. More attention should be paid to the concentration of the coolant. We generally recommend a concentration of 10% to provide sufficient lubricity to ensure proper faucet operation and smooth material removal.
Daguang focuses on providing solutions such as precision CNC machining services (3-axis, 4-axis, 5-axis machining), CNC milling, 3D printing and rapid prototyping services.
