This paper deals with three components of grinding forces related to the incidence of cracks to determine appropriate drilling conditions for smaller cracks, higher processing efficiency, and longer tool life in through-hole drilling of soda-lime glass plates. The crack propagation direction is estimated from the action direction of three components in drilling of glass plates using an electroplated diamond tool. In the drilling process, the components of the x-axis and y-axis increase gradually, and then decrease gradually to zero after piercing a hole at the exit surface. The component of the z-axis increases immediately at the start of drilling, and decreases gradually by the end of drilling after piercing a hole. The component of the z-axis increases with smaller grain size. Thus, the tool approach depth is shallow when the hole pierces. The crack size of the pierced hole is influenced by the component of the z-axis. On the other hand, the crack size of the formed hole from piercing the hole to the end of drilling is influenced by the grain diameter between the tool end and the cylindrical body.