A study on walking phenomenon of drill in drilling aluminum sheet

Abstract

In drilling an aluminum plate by using conventional drills, a strain figure of polygonal shape (having odd number vertexes) was formed in countersinking at the early stage of drilling. The strain figure swiveled with the rotation of the drill in the progress of countersinking and this is called "walking phenomenon of drill."At the drilling stage, when the drill margin was in contact with the material face, the vertexes of the strain figure gave a rotating scar to some depth of the hole wall, and this is called "rifling phenomenon", which caused lowering of drilling accuracy.In this paper, drilling tests were made by using conventional drills on the plates of 9 sorts of aluminum alloys, or 1S, 2S, 3S, etc. The walking phenomenon, or swivelling motion of the polygonal figure, was discussed relating to the progress of drilling starting from the countersinking at the early stage and a relation was obtained between the walking phenomenon and drilling conditions or materials.As the results, the swivelling speed of the polygonal figure depended upon the dimensions of drill and conditions of drilling. The speed was higher with larger angle of chisel edge or higher rotating speed of the drill. In general, it was high for hard materials and became lower for soft materials if the chips were not fully removed. It would be possible to determine the drilling machinability for any materials by the swivelling speed of strain figure.