Indian Standard Specifications for Designated Grades of Fundamental Tolerances

There are various standards established for dimensions and tolerances in the mechanical engineering field. In India, the Bureau of Indian Standards (BIS) sets the standards for the same. One of the important aspects of these standards is the designated grades of fundamental tolerances.

Designated Grades of Fundamental Tolerances

Fundamental tolerances are the basic tolerances that are applied to the dimensions of parts and components. These tolerances are applied to the basic dimensions of a part, such as length, width, height, diameter, etc. The designated grades of fundamental tolerances are used to define the levels of precision required for a particular part or component. These grades are assigned based on the application and the function of the part.

Indian Standard Specifications

According to the Indian Standard Specifications, there are a total of 18 designated grades of fundamental tolerances. These grades are denoted by letters from A to R. Each letter represents a different level of tolerance, with A being the least strict and R being the most strict.

The 18 designated grades of fundamental tolerances are as follows:

- A
- B
- C
- D
- E
- F
- G
- H
- J
- K
- M
- N
- P
- Q
- R
- S
- T
- U

Conclusion

Therefore, the correct answer to the question is option B, which states that there are 18 designated grades of fundamental tolerances according to Indian standard specifications. These grades play a crucial role in ensuring the precision and accuracy of mechanical parts and components.