Studies on the Accuracy in Drilling of Aluminium

Abstract

Generally speaking, the accuracy in drilling is not so high that the drilling is often performed as a rough cutting process. Recently, however, demands for high quality of products and high machining efficiency require the improvement in drilling accuracy. Factors which affect the drilling accuracy are the properties of work materials, drilling conditions, and the accuracy and rigidity of the drilling machine, etc.
In this paper, soft and easy deforming aluminium alloys (6063-O and 6063-F) are used for work materials so that various phenomena may become distinct. Then some experimental studies are reported mainly about the influence of reground drill shape accuracy and drilling conditions, which are the fundamental factors, on the drilled hole accuracy. The accuracy of the drilled hole is evaluated by diameter of hole, cylindrical error, hole shape, etc. The results can be summarized as follows:
(1) The shape of drill tip has a remarkable influence on the diameter and shape of the hole, but not on the cylindrical error.
(2) Increasing the feed deterioates the shape of hole and increases the cylindrical error. But in the case of drilling of annealed material, the margins of drill scratch the wall of hole and the effect of feed becomes complex.
(3) Increasing the diameter of the preliminary hole reduces poth the extension of the drilled hole diameter and the cylindrical error. When the diameter of the preliminary hole exceeds 70% of that of the drilled hole, a desirable hole is obtained.