Machine tools are machines that manufacture different machines and parts. Therefore, the machine tools support all types of manufacturing. And they are known as “mother machines”. When machining by a machine tool, a cutting tool is mounted into a female taper socket. Wear on the inner surface of the female taper which occur when changing tools or during heavy cutting have an influence on the run-out of tool. Therefore, female tapers require periodic maintenance. In the maintenance for female tapers of machine tools, sensory inspection has been standardized in JIS and ISO standards. However, this inspection is impossible to evaluate quantitatively and requires a lot of time. Additionally, this sensory method produces varying accuracies depending on the operators. Therefore, previous studies have proposed a quantitative measurement method which is less dependent on the skill level of the operators. In this previous method, the red lead paint mixed with red lead powder and oil is used to estimate the amount of wear based on the luminance value of the red lead paint. The red lead concentration has a significant influence on the results. In this study, we investigate the influence of red lead concentration through experiments and report the results.