Steel balls for ball bearings are hardened to / » Engineering Materials solved MCQs / By admin Question: Steel balls for ball bearings are hardened to A. 100 VPN B. 400-700 VPN C. 700-800 VPN D. 150-200 VPN Answer» c. 700-800 VPN Note: The above multiple-choice question is for all general and Competitive Exams in India.