The optimal number of working hours in the labor-intensive industry is important to identify the best productivity rate and decrease errors. This research examines the impact of the working hours on the error rate and productivity for three shifts and variability among the shifts in a surface protection manufacturing process. The measurement was taken from the real process and data were analyzed using statistical tools. A strong correlation was found among three-shift productivities. The results showed that there is a slight increase in productivity after the lunch break for all three shifts. A significant difference in productivity has been observed between the first hour and the rest of the day for each shift. The best productivity yield was observed between the 2nd and 7th hour, indicating that longer working hours are less productive and the error rate is increasing. The error rate has a strong positive correlation in the first shift, moderate in the second shift, and weak in the third shift.