The required bell when belling boiler tubes up to but not including 2 inches OD is not less than 1/16" but must not exceed how many inches?

In the context of belling boiler tubes, particularly those with an outer diameter (OD) of up to but not including 2 inches, the standard dictates that the required bell must be significant enough to ensure proper operation and fit. The guidelines specify that the minimum bell diameter is 1/16". However, there is also a maximum limit that ensures that the belling does not excessively deform the tube, which could compromise its structural integrity.

The correct answer indicates that the maximum bell diameter allowed does not exceed 1/8". This size is appropriate as it provides enough expansion for efficient connection while maintaining the strength of the tube. Anything larger, such as 1/4" or 1/2", would surpass recommended limits, potentially leading to issues such as leaks, misalignment, or weakened structure that can occur with excessive belling.

Essentially, adhering to these specifications ensures the safety and functionality of the boiler system, which is critical for its operation and longevity. Understanding these tolerances is crucial for a machinist's mate when performing maintenance or installation tasks related to boiler systems.