Abstract
This paper presents an experimental investigation into the torque-thrust coupling effect in twist drills. A set of cross-coupling stiffness coefficients (Kft and Ktf) are defined. The influence of helix angle on torsional and the cross-coupling stiffnesses is studied. The coupling interaction (as measured by Kft and Ktf) is strongly influenced by the helix angle and has a distinct maxima around 28°. Also, the magnitudes of the coefficients increase parabolically with drill diameter. The pure torsional stiffness also has a maxima around the same helix angle. Under axial restraint, the torsional stiffness increases by 10 to 25% owing to the coupling effect. The larger the torque-thrust interaction, the larger is this increase in torsional stiffness. The findings of this investigation is proposed as a probable basis for the traditional popularity of a 28 to 30° helix angle for drills.
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References
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Bibliography
E.J.A. Armarego and R. H. Brown, ‘The Machining of Metals’, Prentice-Hall, 1969.
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Narasimha, K., Osman, M.O.M., Chandrashekhar, S. et al. An investigation into the influence of helix angle on the torque-thrust coupling effect in twist drills. Int J Adv Manuf Technol 2, 91–105 (1987). https://doi.org/10.1007/BF02601495
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DOI: https://doi.org/10.1007/BF02601495