Question

When a 30-metre chain is tested for its accuracy against a steel tape standardised at 20°C with an 8 kg pull, its overall length should NOT deviate beyond 30 _______.
1. ± 5 mm
2. ± 8 mm
3. ± 10 mm
4. ± 15 mm

Answer 1

Correct Answer - Option 2 : ± 8 mm

Concept:

Chain surveying:

• The measurements in chain surveying are linear.
• Measurements for this survey are taken on the field and other supplementary works like plotting and calculations are carried out in the office.
• Chain, tape, ranging rod, arrows and, cross-staff, Offset rods, Plumb bob are the tools required for chain surveying.

The maximum tolerance(at 20°C with an 8 kg pull) allowable for the metric chain are as follows:

• 05 m chain ⇒ ± 3 mm
• 10 m chain ⇒ ± 3 mm
• 20 m chain ⇒ ± 5 mm
• 30 m chain ⇒ ± 8 mm

​So, When a 30-meter chain is tested for its accuracy against a steel tape standardized at 20°C with an 8 kg pull, its overall length should NOT deviate beyond 30 m ± 8 mm.

Types of the chain are as follows:

• Revenue chain - 33 ft long (16 links)
• Gunter's chain - 66 ft long ( 100 links)
• Engineer's chain - 100 ft long (100 links)
• Metric chain -  30 m (150 links) or 20 m (100 links)