Thread geometries are very important geometries for mechanical design. There are lots of mechanical components that we are using threaded fasteners such as screws, bolts, and nuts. Also, we are using threads in the motion transmission systems. So, you can understand that threads are very important in practical applications. Here, you can find the production techniques of thread geometries; thread cutting, and thread machining operations.
What is Thread Cutting?
In today’s technology, we are using different kinds of thread geometries in different materials. So, a wide variety of manufacturing techniques that we use in threading.
For example, the most important threading application is the thread rolling process. In these processes, there is a negative hard model that creates thread geometries on the surfaces of parts. But in these processes, the materials must be ductile.
Because of these different drawbacks, we need a machining process to produce threaded geometries from hard materials in a serial production manner.
External Thread Cutting
Above all, the most important application of thread cutting is external threading on lathe machines. There is a tool that has the same shape as the thread grooves. There is a cylindrical part that is attached to the lathe machine. The cutting tool starts to cut spiral types on the part. With the rotation of the part and the feed motion of the cutting tool, we obtain these geometries.
In general, we do not obtain the complete threaded geometry on the surface of the cylindrical part in one pass. We are using several passes to obtain a thread geometry. In each pass, the depth of the cut increases.
Also, the most important drawback of the external thread cutting is, that it is applicable for medium production sizes.
Thread Milling Operations
Another important process to produce external threads is thread milling processes. In the cutting of the threads, we use the milling operation. In these operations, there is a milling cutter that is oriented at the helix angle. And makes the feeding motion parallel to the cylindrical shape.
This cylindrical shape rotates, and we obtain the thread geometry on the cylinder.
The most important advantages of the thread milling operations;
- We can obtain the big threads with thread milling operations.
- Much more accurate and smooth geometries are obtained. So, the surface characteristics of thread milling operations are better than others.
Thread Cutting Dies
To decrease the total manufacturing time in the thread cutting in single-point lathes, they generally use threading dies. Inside these threading dies, there is a tapered multi-toothed die. With this structure, we can obtain a threaded geometry with one pass.
Also, the taper provides the opening of the threads more smoother. So with the increasing depth, the threaded geometry will get deeper.
Furthermore, we use these dies for manual operation. We need to detach the thread-cutting dies manually. This is risky and we can damage the thread geometry. Maybe this is the most important drawback of these dies.
Thread Chasing Operations
Also, there is a solution for this manual detachment of the threading die. We can use the self-opening dies to detach the die easily from the part. So, after the thread cutting operation, we can open the die.
The other disadvantage of the thread cutting dies, we need to have different kinds of sizes for each thread standard.
And also, the application of the self-opening dies is in two configurations. The rotation movement is performed by the dies or tool.
Thread Grinding Operations
Another important thread cutting application is thread grinding. The thread grinding is nearly the same as the thread milling operations. But the rotational speeds of the grinding tool are greater than the milling.
Also, we can use the thread grinding operations to apply surface finish on the produced threaded geometries.
Internal Thread Cutting
Also, internal threads are very important for nut geometries. We use the external threads to attach them to the internal thread geometries. The production approach internal thread cutting operations are quite different from the external threads.
The most common application in the internal thread cutting is the tapping operations. In the tapping, the internal thread geometries are obtained by the external threaded tool. This external threaded tool which is also called a tap creates the internal threads by rotating inside the hole. Also, the diameter of the tap is equal to the minor diameter of the hole.
Furthermore, the edge section of the tap is tapered to make it easy to tapping applications. We can detach the tapping tool from the work part by rotating it in reverse. Also, we generally use drill presses to apply tapping operations.
Like the thread chasing operations, we can use the collapsible taps to eliminate the detachment time of the tool from the workpieces. Also, it is risky that the tool can damage the workpiece while reverse rotating. These collapsible taps can be retracted easily from the tool.
Tapping with Other Machines
Apart from the drill presses, we can use the taps on other machines such as turning and milling. With the use of other kinds of machines, we can obtain more rapid productions of threaded geometries. For example, with the use of the gang drill machine, we can make multiple thread cutting at the same time. Also, turning operations with tapping tools can enhance the total machining times.
Advantages and Disadvantages of Thread Cutting Operations
Like the other manufacturing methods, we need to consider the general advantages and disadvantages of the thread cutting operations.
- The most important advantage of these operations, there are different kinds of operations that we can apply according to our needs. For different production rates and sizes, there are different operations are available.
- These operations are applicable in the serial production of threads. With the proper operation and machine, we can produce threaded geometries in a serial production manner.
- In general, we do not require a skilled workforce for the thread cutting operations which means lower production costs of thread geometries.
- Tooling costs may be a problematic issue in these operations. Because we are using special tools to produce different kinds and standards of threads.
- Because of the manual applications, production faults take place commonly. So, this means higher scraps.
So, as you see above, there is a wide variety of thread-cutting operations. According to your needs, you can select and apply one of these applications.
Threads are very important geometries. We use them in different machinery applications. Screws may be the most important example. We divide these operations as external and internal thread cutting.
In external cutting the most important application is the single point cutting in lathe machines. Also, there are other variations are available. And also, we use tapping operations to obtain internal threads.
While we are selecting a proper cutting operation, we need to consider the advantages and disadvantages of the processes. Because we need to be aware of the drawbacks to take precautions and consider the financial sides of them.
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FAQs About Thread Cutting
Because, thread geometries are very important in such applications; as bolts and nuts, screws, and other motion transmission applications. So without these geometries, we can not build machinery for our society.
There are different kinds of thread cutters. Around these cutters; are thread milling tools, single point lathe threading tools, thread cutting dies, and taps for tapping operations. Also, grinding is very important for thread cutting.
It is very simple to understand. There is a single-point cutting tool. This tool is making a forward motion. And also the workpiece is rotating. So, with the combination of these two motions, we obtain the thread geometries.
There are different types of thread cutting operations; internal thread cutting and external thread cutting. We perform the internal threads cutting operations with tapping operations. Also, we make the external thread cutting with lathes and thread cutting dies.
The thread cutting is obtaining threaded geometries on the cylindrical parts both internally and externally.
Because these operations provide better suitability to the serial production with the comparison of thread rolling and casting operations.
These two operations are the machining operations. But in rolling, the cylindrical shapes are rolled between the threaded tools. In these operations, we use machining tools directly.