The assembly of aeronautical parts requires the machining of composite materials. Drilling is the most important process in the assembly. When drilling composite materials, a number of defects are generating. A solution, to reduce these defects, is to drill using a step gundrill. In this paper, drilling of thick composite plates using a step gundrill is studied. Delamination, which is considered the major drilling defect, is analytically modelled at the hole exit. The critical thrust force at delamination is then found dividing the plate under the tool into several zones corresponding to the tool active part. These results are experimentally validated. The optimal cutting conditions at delamination are finally determined using a cutting force model. This model uses the same zones decomposition as the analytical critical thrust force model. The results of this paper can be extended to other tools to find the optimal cutting conditions corresponding for delamination-free drilling.

航空零件的组装需要复合材料的加工。钻孔是组装中最重要的过程。在钻复合材料时，会产生许多缺陷。为了减少这些缺陷，一种解决方案是使用阶梯枪钻进行钻孔。在本文中，研究了使用阶梯式枪钻对厚的复合材料板进行钻孔。被认为是主要钻孔缺陷的分层是在孔出口处进行解析建模的。然后发现分层时的临界推力将工具下方的板划分为与工具活动部件相对应的几个区域。这些结果经过实验验证。最终，使用切割力模型确定分层时的最佳切割条件。该模型使用与解析临界推力模型相同的区域分解。