Revolutions Per Minute Formula |
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\( RPM \;=\; \dfrac{ SFM \cdot 3.82 }{ D }\) (Revolutions per Minute) \( SFM \;=\; \dfrac{ RPM \cdot D }{ 3.82 }\) \( D \;=\; \dfrac{ SFM \cdot 3.82 }{ RPM }\) |
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| Symbol | English | Metric |
| \( RPM \) = Revolutions per Minute | \(rev\;/\;min\) | - |
| \( SFM \) = Surface Feet per Minute | \(ft\;/\;min\) | - |
| \( 3.82 \) = Industry Constant | \(constant\) | - |
| \( D \) = Tool Diameter | \(in\) | - |
Revolutions per minute, abbreviated as RPM, is the number of complete rotations that a machining tool, such as a lathe or milling machine, makes in one minute while performing a cutting operation. RPM is a critical parameter in machining because it directly affects the cutting speed, tool life, and surface finish of the workpiece. Machining at the correct RPM is crucial for achieving optimal performance. Too high of an RPM may lead to excessive tool wear, reduced tool life, and poor surface finish. On the other hand, too low of an RPM may result in inefficient cutting, increased cutting forces, and heat generation.
Machinists use charts, formulas, or software to determine the appropriate RPM for a given machining operation based on the cutting tool, material, and desired results. It's part of the broader concept of cutting speeds and feeds, which involves optimizing the parameters to achieve efficient and effective metal removal during machining processes.
