1) Cumulative Errors
2) Compensating Errors
1) Commutative Errors
The errors which occur in the same direction and tend to accumulate, or to add up, are called cumulative Errors/ Such an error makes the apparent measurements always either too long or too short.
a) Positive Commutative Error: Measures length more than the actual length .
Eg: Knots in connecting links, incorrect alignment, working in windy weather etc.
b) Negative Cumulative Error: Measures length less than the actual length.
Eg: Flattening of connecting ribs, opening of ring joints etc.
2) Compensating Error
The error which are liable to occur in either direction and tend to compensate are called compensating errors. These are caused in the following situations:
a) Incorrect holding of the chain
b) The chain is not uniformly calibrated throughout its length.
c) Refinement is not made in plumping during stepping method.