The assembly process of aerospace components involved the machining of a large number of countersunk holes， with the depth of the countersunk holes being a critical technical parameter that required precise control， significantly impacting the quality of component assembly. Helical milling was a new method for drilling assembly holes that had emerged in recent years， and when combined with specialized tools， it could also be used for the machining of countersunk holes. Based on existing portable helical milling equipment， this paper proposed an automatic control method for the depth of countersunk hole machining. First， a spiral milling test platform was established to analyze the sources of error during the machining process. Then， through theoretical analysis and tool contact force measurement experiments， a functional relationship between the contact force and the feed motor torque value was established， and the optimal tooling parameters for machining with a milling and countersinking integrated tool were further determined. Finally， automatic tooling and countersinking machining experiments were conducted on titanium alloy test pieces， and the countersink depth was measured. The results show that the depth error of the countersunk holes after machining is controlled within 0.05 mm， meeting the design accuracy requirements of the components.