One of the major principles of Lean Manufacturing consists in only producing what is really needed by the customer. Despite a certain infatuation with this process, in the bar turning sector companies tend to produce more than the real demand. This production strategy can be explained by the desire of these companies to redeem their high changeover costs which are difficult to compress. In light of this context, our aim was to provide decision-making factors to find out the limits of this policy. To do this, we developed an analytical model based on calculating the total cost of producing the ordered parts and those manufactured in addition to the demand. This calculation has the advantage of taking into account both economic constraints, production means and sales opportunities. The introduction of a probabilistic model for estimating potential sales has also allowed us to consider the impact of the risk of non-sale on the total cost of production. Orienting bar turning companies towards a single strategy for all their production is complicated, this strategy has to be adapted to each case.