Woodturning RPM Lathe Calculator
Determine the safe starting RPM for turning unbalanced wood blanks.
Safety is paramount in woodturning, and it starts with setting the correct lathe speed. Spinning a large, heavy, unbalanced blank of wood too quickly can cause catastrophic failure, sending pieces flying with dangerous force. This calculator provides a safe maximum starting RPM based on a widely accepted rule of thumb.
The principle is simple: the larger the diameter of the workpiece, the slower it must spin to be safe. This calculator uses the formula `(6000 to 9000) / Diameter` to give you a conservative speed. Once the blank is rounded and balanced, you can safely increase the RPM for smoother cutting.
The calculation is a simple rule of thumb used by woodturners everywhere.
- Measure Max Diameter: Find the largest diameter of your rough, unbalanced blank in inches.
- Apply the Formula: The calculator divides a constant (typically between 6000 and 9000) by the diameter to find the recommended maximum starting RPM. We use a constant of 8000 for a safe, middle-of-the-road estimate.
RPM = 8000 / Diameter (in)
- RPM (Revolutions Per Minute): The speed at which the lathe's headstock and the workpiece are spinning.
- Blank: The rough, often unbalanced piece of wood that you mount on the lathe to begin turning.
- Catch: A dangerous event where the turning tool digs too deeply into the wood, which can shatter the workpiece or wrench the tool from your hands. Proper speed and tool presentation help prevent catches.
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Always double-check your measurements before cutting.
Account for the kerf (the width of the saw blade) in your calculations.
Consider wood movement (expansion and contraction) in your final dimensions.
Buy 10-15% extra material to account for mistakes and waste.