Several approaches can be used to find defects in metal surfaces. Eddy current testing is a simple and efficient method for non-destructive testing of metals, identifying alloys, measuring coating thickness, and detecting corrosion. Impedance spectroscopy enables depth profiling and high-speed measurements in real-time manufacturing. For example, in the wood processing industry, early detection of cracks in high-speed band saws is crucial. Electromagnetic testing, particularly eddy-current-based methods, is widely used. This paper reviews existing solutions and investigates cracked saw blade specimens using planar coils in the 100 kHz–10 MHz range. Results show that higher frequencies improve crack detection. Future research should focus on high-speed detection and machine vision-based solutions.