In the study of the wear mechanisms, the f_ab factor became an important tool in the quantification of the slip response of a particle on a surface as to the ability to groove or cut. However, the f_ab values ​​are usually associated with a low repeatability, making it impossible in some cases to associate them with the different abrasion mechanisms verified or until their invalidation. One practice often used to decrease standard deviation values ​​is to increase the number of measurements. Thus, the present work aims to identify the number of measurements needed to obtain the f_ab factor with better repeatability. Six sample sizes were considered: 5, 10, 15, 20, 25 and 30. The results obtained showed that the sample size significantly influenced the mean values ​​and the repeatability of the f_ab values.