When evaluating hand injection moulding machines, you must focus on the shot capacity (grams/ounces) to ensure it meets your part volume requirements. Key mechanical specs include the clamping force, which prevents flash during injection, and the maximum mold dimensions the machine can accommodate. For precision, look for units with digital PID temperature controllers to maintain consistent melt flow, and ensure the heating power (Watts) is sufficient for the specific resins (like PP, PE, or ABS) you intend to use.