As per IS 3129-1985, the permissible tolerance for the length of finished boards shall be:
Try it first: pick an option, then read the explanation.
The Importance of Tolerance in Manufacturing
In manufacturing, it's impossible to produce every single item to an exact dimension. A tolerance is the permissible limit of variation in a physical dimension. It defines the acceptable range between the maximum and minimum allowable size for a part to still be functional.
The Bureau of Indian Standards (BIS) publishes codes like IS 3129-1985 to standardize these tolerances for building materials. This ensures that finished boards from different manufacturers will be consistent and fit together properly during construction.
Detailed Analysis of the Options
The question asks for a specific tolerance value from the Indian Standard code for particle boards. Let's look at the specifications.
(a) ±6 mm, (b) ±2 mm, and (d) ±4 mm
These are incorrect values for the length tolerance according to the specified IS code. While they might be tolerances for other dimensions or other materials, they do not apply to the length of finished boards under IS 3129-1985.
(c) ±8 mm
This is the correct answer. As per IS 3129-1985, which specifies the standards for particle boards, the permissible tolerance for both the length and width of finished boards is ±8 mm. The tolerances for thickness are much smaller. Here is the full breakdown:
| Dimension | Nominal Size | Tolerance |
|---|---|---|
| Length | For all lengths | ±8 mm |
| Width | For all widths | ±8 mm |
| Thickness | Above 25mm | ±1 mm |
| Up to 25mm | ±0.8 mm |
Quick Summary of Tolerances (IS 3129-1985)
| Dimension | Permissible Tolerance |
|---|---|
| Length | ±8 mm |
| Width | ±8 mm |
| Thickness (≤ 25mm) | ±0.8 mm |
| Thickness (> 25mm) | ±1 mm |
Study Tips
- Remember the "Rule of 8": For finished boards under this IS code, the tolerance for both Length and Width is the same: ±8 mm. This makes it easier to remember.
- Thickness is Tighter: Notice that the tolerance for thickness is much smaller (around ±1 mm). This is because thickness is often more critical for a flush fit and finish.
- Know the Code: Associate these values with IS 3129-1985, which deals with particle boards. Different materials will have different IS codes and different tolerances.