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There are two basic methods (that I know about). They are ...

1. Threads can be cut. They may be cut with a pointed tool in a lathe, or the may be cut with a die that is rotated relative to the material to be threaded. In either case, the result is sharp, clean threads. In particular, they have a sharp V at the bottom which can serve as a stress raiser.

2. Threads may be formed by rolling. This is essentially material deformation under load applied with a rolling tool. Such threads are usually not nearly as sharp as cut threads, but they have superior strength and lack the sharp V stress raiser.

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Perhaps, you are limiting your self to machining processes to which we could 

add thread grinding using grinding wheels in process similar to turning, EDMing external threads with split mirror electrodes and with CNC controlled machining is now standard to use threading end mills for internal and external threads.

Consider also molded threads like in plastic devices and bottles, that could be achieved through plastic injection molding, which also is the basis for sintered components which are basically a mixture of metal particles held on a resin base which is molded into parts and later are heated to melt and compact the metal particles together and the resin is separated leaving a solid metal part

And with 3D printing now could be achieved any kind of internal and external forms including threads

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On 19/05/2015, 02:43:29, DrD said:

There are two basic methods (that I know about). They are ...

1. Threads can be cut. They may be cut with a pointed tool in a lathe, or the may be cut with a die that is rotated relative to the material to be threaded. In either case, the result is sharp, clean threads. In particular, they have a sharp V at the bottom which can serve as a stress raiser.

2. Threads may be formed by rolling. This is essentially material deformation under load applied with a rolling tool. Such threads are usually not nearly as sharp as cut threads, but they have superior strength and lack the sharp V stress raiser.

Drd Sir, you forgot "molding" this process is the most common in plastic components.

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Dear SJJ,

Please note that I qualified my remarks with (that I know about). I have done very little (like nothing!) with plastics, so I don't think much about them.

That said, I'm sure you are correct about molding plastic threads. It makes sense.

DrD

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External threads can be made in various methods 

1. Single point tool.

2. Thread rolling

3. Dies especially for smaller diameter size components. 

4.Thread grinding for precision threads in shafts 

5.Injection moulding for plastic parts like bottles .

 

 

 

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Thread cutting can be done commonly in lathe machine but in high capacity thread cutting lendis machine is used . Lendis machine has a chuck like lathe machine ,the chuck used in the lendis is a self centering chuck which has 3 quarterly cut high speed steel thread cast die which opposes the metal and Mark the thread at the surface .

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