Small and Medium-sized Enterprises operating legacy stamping presses often lack affordable diagnostics, risking undetected tool damage. This study proposes a frugal vibroacoustic retrofitting methodology using a low-cost piezoelectric sensor and edge processing. Experiments compared normal blanking (0.5 mm brass) with simulated double-hits (0.1 mm spacer). Analyses revealed that abnormal events generate distinct, highly impulsive transients with shorter post-impact signal persistence and elevated broadband energy including mid- and high-frequency components. Unsupervised clustering confirmed reliable detection using simple features despite partial signal overlap. The approach enables cost-effective tool protection and sustainable asset life-extension, supporting Zero-Defect Manufacturing in resource-constrained environments.