Length to Diameter Ratio for CNC Turning

The length to diameter ratio is an important consideration when designing CNC turned parts. The general rule of thumb is that the length-to-diameter ratio should not be greater than 5. Excessive force will be applied to a part that is unable to support it, resulting in failure.
Because the length has a much larger impact on the deflection of the part at smaller diameters, an even smaller length-to-diameter ratio is required. Increased pressure on slender parts increases the likelihood of failure.