To obtain the maximum permissible clearance, what should be done with the difference between the pipe and the fitting?

To obtain the maximum permissible clearance between the pipe and the fitting in silver brazing, the appropriate action is to subtract the inside diameter (ID) of the pipe from the outside diameter (OD) of the fitting. This calculation is essential because it allows for an accurate measurement of the gap or clearance that is necessary for effective brazing.

When brazing, having the correct clearance ensures that the filler metal can flow properly into the joint and form a strong bond. If the clearance is too small, there may not be enough space for the filler metal to be absorbed effectively, leading to a weak joint. Conversely, if the clearance is too large, it may result in inadequate bonding and a potential failure of the joint under stress.

By subtracting the ID of the pipe from the OD of the fitting, you are directly measuring the gap available for the brazing material, which determines whether the joint will allow for optimum filler penetration and structural integrity. This method is fundamental in ensuring that the assembly is correct before proceeding with the brazing process.