The aim of this study was to evaluation of maximal acceptance insertion force (MAIF) and prefer insertion force (PIF) by field connecter assembly workers. Specifically, a psychophysical methodology was used in which participants were asked apply MAIF and PIF that were considered acceptable over a period of eight hours given combination of hand posture, age, and work period in simulated insertion task. Data were collected from 20 male in field connecter assembly workers. The experimental measurement setup included a one-direction load cell, a spring, a knob, and a flame to evaluate MAIF and PIF. The independent variables were five hand posture, three age group, and three work period group. The results of ANOVA for MAIF indicated the main effect of hand posture (p < 0.0001), and age (p = 0.0049). The results indicated that hand posture (p < 0.0001), and work period (p = 0.005) significantly affected PIF. It means that hand posture is very important factors for determination of insertion force. As a results of this study, PIF showed a decrease of about 32% compared to MAIF. In this study, it is recommended to consider hand posture, age, and prefer force when determining the insertion force.