0 votes 0 votes In a machining operation, if the generatrix and directrix both are straight lines, the surface obtained is cylindrical helical helical surface of revolution Materials, Manufacturing and Industrial Engineering gateme-2015-set3 materials-manufacturing-and-industrial-engineering + – Arjun asked Feb 24, 2017 • recategorized Mar 4, 2021 by Lakshman Bhaiya ♦Arjun 28.5k points answer See all 0 reply