We consider the problem of the automatic inspection of industrial metal pieces. The purpose of the work presented in this paper is to derive a method for defect detection. For the first time in this context we adapt level set method to distinguish hollow regions in the metal pieces from the grinded surface. We compare this method with Canny edge enhancement and with a thresholding method based on histogram computation. The experiments performed on two industrial images show that the proposed method retrieves correctly fuzzy contours and is robust against noise.