How to cut pipe threads on a cnc lathe

Written by christian mullen
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How to cut pipe threads on a cnc lathe
CNC lathes are ideal for cutting threads. (Lathe Turning Stainless Steel image by Stana from

One of the major advantages of a CNC, or computer numerical control, lathe is the ease of threading. In order to make pipe threads, you must program the parameters of the thread itself and inform the machine of what tooling you will use for the threading process. Performing this operation on a CNC can ensure accuracy of the cutting process and make sure that the pipe threads you do cut are accurate and snug according to the dimensions on the blueprint.

Skill level:

Things you need

  • Threading tool

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  1. 1

    Insert the rod material into the chuck. Make sure that it is snug and that no slipping will occur during machining. Set the zero at the end of the material by bringing a tool tip close to the end of the rod and resetting the zero point on the main home page of the CNC lathe control.

  2. 2

    Write the program to cut the pipe threads in the CNC lathe. CNC lathes are capable of cutting any type of threads, including pipe threads using G code or conversational language. G code is a standardised language that can be used on all CNC machines, and conversational languages are those created by the manufacturer and can often only be used with their machines.

  3. 3

    Set the program to machine the major diameter of the pipe threads. This is the outside diameter of the threads after they have been cut. The machine will turn the material to just above this number and allow the threading tool to take it down to the final dimension.

  4. 4

    Set the program to cut the relief for the threads. This is the area just beyond the threaded area and is necessary as the threading tool travels about .15 inch past the main threaded areas it cuts. The diameter of the relief will be less than the minor diameter used for the threaded area. You can use a cut of tool to machine this section.

  5. 5

    Set the dimensions of the thread in the program. You must make the machine aware of the threading tool used for the program as well as the pitch diameter of the thread and the amount of threads per inch. The threading tool will make a roughing and a finishing pass top complete the pipe threads. If the pipe threads are metric, you may have to convert that dimension to standard or vice versa.

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