Cutting edge control by monitoring the tapping torque of new and resharpened tapping tools in Inconel 718

In aerospace industry, tapping is the prime choice for hole threading in jet aero-engine turbine components. Taps are not usually resharpened, unlike other tools which indeed are resharpened once they have accomplished a certain number of cycles of service. Instead, cutting taps are discarded when they reach a certain number of threaded holes. The waste of cutting tools and the timing for tool replacement is computed in the cost expenses of the end part. In order to reduce manufacturing waste, this work focuses on studying different tapping configurations, to prove the feasibility of resharpening in the interest of extending the tap's service life. Tapping experiments are performed in Inconel 718 under several conditions: (a) resharpened taps, (b) resharpened and recoated taps, (c) an additional 2 degrees chamfer clearance angle taps and (d) as-received taps (baseline). The results show that the three-time resharpened taps increased their lifespan up to 200%. Tap's performance is analyzed considering several criteria: checking by Go/No-Go gauges, evaluating the flaking or notching of cutting edges, measuring axial forces and torques, and analyzing the surface integrity of the threaded holes. Therefore, monitoring the cutting forces and torque during tapping helps us to anticipate to the tool's fracture; and controlling the crest edge roundness progression is crucial for having an accurate thread tolerance and the desired surface integrity.