This question was previously asked in

AAI JE (Technical) Official Paper 2018

Option 4 : 16i

ST 2: Strength of materials

2026

15 Questions
15 Marks
15 Mins

__ Explanation__:

**Tolerance grade**:

- In a standardized system of limits, lower is the tolerance value, lower is the grade of tolerance number but more precision is the component.
- The Bureau of Indian Standards (BIS) specifies
**18 basic tolerance grade numbered IT01, IT0, IT1, IT2, to IT16**. - The
**commonly used**tolerance grades for machine components are from**IT5 to IT14**and expressed in terms of tolerance grade '**i**', which is a function of geometric mean diameter (D in mm) of the various diameter ranges as per the standard.

\(i\; = \;0.45\sqrt[3]{D}\; + \;0.001D\;\) in μm

D = D1 x D2

D1 and D2 are the nominal sizes marking the beginning and the end of a range of sizes, in mm.

Some important grade and their tolerance value are given in the table below.

Grade | Tolerance |

IT5 | 7i |

IT6 | 10i |

IT7 | 16i |

IT8 | 25i |

IT9 | 40i |

IT10 | 64i |

IT11 | 100i |

IT12 | 160i |

IT13 | 250i |

IT14 | 400i |

IT15 | 640i |

IT16 | 1000i |

__Alternate Method__

The value of tolerance grade can be found by,

\(10{\left( {1.6} \right)^{\left( {ITn - IT6} \right)}}\)

Here, the value for the tolerance grade IT-7 is:

\(10{\left( {1.6} \right)^{\left( {IT7 - IT6} \right)}}=10\times 1.6=16i\)

where i is the standard tolerance unit or fundamental tolerance unit.