Selecting a VMC requires matching machine capabilities to your specific workpieces. Key factors include Spindle Speed (RPM), where 8,000-12,000 RPM is standard for aluminum while high-torque spindles are needed for steel. You must evaluate the Travel Size (X/Y/Z axes) to ensure it accommodates your largest parts, and prioritize BT40 or BT50 taper interfaces depending on the required rigidity. For high-precision industries like aerospace or medical, look for machines with linear scales and high-precision ball screws to maintain tolerances within ±0.005mm.