Leaving machining allowances on parts is important for many practical reasons. This section discusses the reasons why this is a common engineering practice.
Dimensional Accuracy: Leaving machining allowances on parts gives machinists a safety margin to perform finish machining operations. By leveraging cutting parameters like high speeds and low depths of cut, they can achieve high dimensional accuracy during the final cuts.
Surface Finish: As with dimensional accuracy, having extra material on the workpiece surface allows machinists to manage the surface quality during the finishing cuts.
Quality Control: Machining allowances also encourage in-process quality control. Engineers get a chance to monitor the production quality between roughing and finishing cycles and update their manufacturing plans accordingly, leading to fewer part rejections.
