Spindle Speed Formula |
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\( s_s \;=\; s_c \cdot d \cdot \pi \) (Spindle Speed) \( s_c \;=\; \dfrac{ s_s }{ d \cdot \pi }\) \( d \;=\; \dfrac{ s_s }{ s_c \cdot \pi }\) |
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| Symbol | English | Metric |
| \( s_s \) = Spindle Speed (RPM) | \(rev\;/\;min\) | \(rev\;/\;min\) |
| \( s_c \) = Cutting Speed (SFM) | \(ft\;/\;min\) | \(m\;/\;min\) |
| \( \pi \) = Pi | \(3.141 592 653 ...\) | \(3.141 592 653 ...\) |
| \( d \) = Tool Diameter | \(in\) | \(mm\) |
Spindle speed is the rotational speed of a machine’s spindle. In machining, the spindle holds the cutting tool (like a drill bit or milling cutter) and spins it at a set speed to cut or shape the workpiece. The spindle speed is crucial because it directly impacts the cutting conditions, tool life, surface finish, and efficiency of the machining process. Selecting the right spindle speed requires balancing speed, tool life, and quality of finish. Testing and adjusting speeds to account for machine limitations, material variability, and tool condition are common in practice to achieve optimal machining results.
