A Novel Approach to the Design of Self-Piloting Drills With External Chip Removal, Part 1: Geometry of the Cutting Tip and Grinding Process

Abstract

The performance of a self-piloting drill with external chip removal is affected by the geometry of its cutting tip. A comprehensive analysis of the cutting tip geometry and its influence on the drill performance is made. This subject is treated in two parts. In Part 1, the cutting tip geometry is analyzed. Special attention is given to the flank planes and a novel approach to the design of the drill was developed. By this approach the drill flank planes are located with minimum offset of the supporting pads’ faces relative to the plane of the drill corner’s rotation. Since several important drill angles are defined, the analysis is extended to cover the grinding process. The experimental comparison between the ordinary and newly designed self-piloting drills with external chip removal is also made to show the advantages of the latter.

Investigation of Chip Deformation and Breaking with a Staggered Teeth BTA Tool in Deep Hole Drilling

“…where Ph is the pitch of the chip flow, R is the maximum cutting radius of the tooth, vR is the chip flowing velocity on the maximum cutting radius, vR = wRtC0/tCR, and tcR is the chip thickness on the maximum cutting radius. By substituting Equations (6) and 7into Equation 5, the chip thickness along the cutting radius can be obtained as follows: Assuming that the same volume for the chip formed and for the workpiece material removed, the chip thickness flowing out on the cutting radius r is as follows:…”

“…It is commonly applied in high-precision and high length-to-diameter ratio deep hole machining, e.g., in the fields of new energy, aerospace, and the military [3,4]. Due to the limitation of the chip removal channel area, the problem of chip breaking and evacuation is always a bottleneck in deep hole drilling, which is particularly difficult when drilling low-carbon alloy steel materials such as nuclear power tube-sheets, with strong toughness and plasticity [5][6][7][8]. In BTA deep hole drilling, if the size of the chip formation is not very regular and perfect, it might not guarantee smooth evacuation of the chip, which would lead to clogging of the chip removal channel, weakening of the cooling effect, increased drilling torque, and failure of the drill.…”

Deep-hole Tools

“…5.81), but as one of the most important design parameters. The location distance of the cutting edge with respect to the y 0 -axis of the tool coordinate system defines the distribution of the rake angles along the cutting edge [20]. Therefore, the influence of this parameter on tool life should be considered from this viewpoint.…”