Calculate threading RPM, thread pitch, feed rate, cutting speed, and pitch diameter for taps, thread mills, and standard threads in metric or inch units.
Threading RPM Formula
The following formula is used to calculate the threading RPM (Revolutions Per Minute). Variables:
RPM = \frac{CS \times 12}{\pi \times D}- RPM is the threading speed in revolutions per minute
- CS is the cutting speed (surface speed) in feet per minute
- D is the workpiece diameter in inches
To calculate the threading RPM, multiply the cutting speed by 12 to convert feet per minute to inches per minute, then divide by (π × D). (If using metric units, the equivalent form is RPM = (CS × 1000) / (π × D) with CS in m/min and D in mm.)
What is a Threading RPM?
Threading RPM (Revolutions Per Minute) refers to the speed at which a tool or machine, typically a lathe or milling machine, rotates when cutting threads into a material. The RPM is a crucial factor in threading as it impacts the quality of the threads and the tool’s lifespan. It is determined based on the material being threaded, the type of tool being used, and the diameter at which the cut is being made.
How to Calculate Threading RPM?
The following steps outline how to calculate the Threading RPM.
- First, determine the cutting speed (CS) in feet per minute.
- Next, determine the workpiece diameter (D) in inches.
- Next, use the formula RPM = (CS × 12) / (π × D) to calculate the Threading RPM.
- Finally, calculate the Threading RPM.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Cutting speed (CS) = 120 feet per minute
Workpiece diameter (D) = 1 inch. RPM = (120 × 12) / (π × 1) ≈ 458.37 RPM.
