Threading RPM Calculator


Calculating threading RPM (Revolutions Per Minute) is crucial in machining operations. Whether you’re working on a lathe, mill, or any other machine tool, understanding the RPM required for threading operations is vital for precision and efficiency. To simplify this process, a calculator can be immensely helpful. Below, we’ll discuss how to use and implement such a calculator.

How to Use

Simply input the required parameters into the calculator fields, such as the spindle speed (S), number of threads per inch (TPI), and thread pitch diameter (D). Then, click the “Calculate” button to obtain the RPM for threading.


The formula for calculating threading RPM is:


  • RPM = Revolutions per minute
  • CS = Cutting speed (in SFM or surface feet per minute)
  • N = Number of threads per inch (TPI)
  • D = Thread pitch diameter (in inches)

Example Solve

Let’s say we have a cutting speed (CS) of 200 SFM, 8 threads per inch (N), and a thread pitch diameter (D) of 0.5 inches.

Using the formula:


So, the threading RPM would be 3200.


Q: What is Cutting Speed (CS)?
A: Cutting speed refers to the surface speed of the workpiece in feet per minute while machining.

Q: Why is Thread Pitch Diameter (D) important?
A: Thread pitch diameter is crucial as it represents the effective diameter of the thread, affecting the RPM calculation significantly.

Q: Can this calculator be used for metric threading as well?
A: Yes, the calculator can be adapted for metric threading by inputting the relevant parameters in metric units.


Calculating threading RPM is essential for machining precision threads. By using the provided formula and implementing a calculator, machinists can streamline this process and ensure accurate RPM values for their threading operations.

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