Title: The influence of drill geometric accuracy on steady tool wear development and catastrophic tool failure in high aspect ratio gundrilling of Inconel-718

Authors: Keng Soon Woon; Shigeyuki Kanno; Kui Liu

Addresses: Machining Technology Group, Singapore Institute of Manufacturing Technology, 71, Nanyang Drive, Singapore 638075, Singapore ' Machining Technology Group, Singapore Institute of Manufacturing Technology, 71, Nanyang Drive, Singapore 638075, Singapore ' Machining Technology Group, Singapore Institute of Manufacturing Technology, 71, Nanyang Drive, Singapore 638075, Singapore

Abstract: The performance of gundrilling and its stability are governed by the accuracy and repeatability of critical drill geometries for precision self-guiding such as the inner approach angle, outer approach angle and drill apex. Through a performance evaluation study of Inconel-718 drilling, it was determined that inaccurate approach angles with large geometric errors could deflect and bent the rotating drill in both radial and axial directions, resulted in severe whipping and vibrations that damage the carbide drill tips. As the deflected drill is advanced continuously, the drill apex deviates towards other directions from the original drilling path, leading to the formation of sectional straightness error. Consequently, accumulation of multiple sectional errors of each drilling cycle throughout an exhaustive deep hole drilling operation induces irrecoverable straightness misalignment on the hole.

Keywords: nickel chromium based superalloys; oilfield equipment; tool wear; tool failure; manual grinding; oil industry; drill geometry; geometric accuracy; high aspect ratio gundrilling; Inconel-718; precision self-guiding; deep hole drilling; carbide drill tips; whipping; vibration; straightness misalignment; straightness errors.

DOI: 10.1504/IJAT.2013.053164

International Journal of Abrasive Technology, 2013 Vol.6 No.1, pp.1 - 15

Received: 19 Sep 2012
Accepted: 21 Nov 2012
Published online: 05 Jul 2014 *

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