This API standard specifies requirements for the qualification of suppliers of machining services where API product standards require such services, or are otherwise specified as a requirement for compliance. Compliance with this standard is not required to demonstrate compliance with any other API standard or specification.

This standard establishes the requirements for three machining qualification levels (MQL 1, MQL 2, and MQL 3). These three MQL designations define different levels of quality and qualification requirements. They are numbered in increasing levels of requirements in order to reflect increasing quality and qualification criteria.

Final assembly, component testing (e.g. nondestructive examination, pressure testing), or a broker of machining services are outside the scope of this standard.

This standard applies when specified by the customer or voluntarily followed by the machining services supplier.