Multiple choice general knowledge science & technology

If a mechanical bolt has a marking of class 12.9 what do the numbers 12 & 9 indiacte

  1. Month and Year of manufacture

  2. Head dia and Shank dia

  3. Mechanical property - Ultimate tensile strength and Yield strength

  4. hardness and surface finish
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In bolt grading systems like ISO 898, class 12.9 means: 12 = ultimate tensile strength (1200 MPa minimum, first digit × 100), 9 = yield strength ratio (90% of ultimate tensile strength, second digit × 10%). This is standard mechanical engineering notation for bolt strength properties.

Keep practicing — related questions