Possibly one for Pete (or other older tool tarts)

[Dustydazzler]

What does the AF on an old spanner stand for ??

 

[snowhead]

Across Flats
And it's not just old spanners, it's still current for U.N.F and U.N.C threaded bolts /nuts.

 

[Pete999]

What does the AF on an old spanner stand for ??

What are AF spanners - https://www.answers.com/Q/What_are_AF_spanners thought at first it Meant American Fred, but common sense kicked in.

 

[netblindpaul]

AF still applies to metric as well as UN/SAE sized spanners it as has been said refers to the jaw size, which is the across flats dimension of the hexagon of the nut, so a 13mm spanner will fit a 13mm AF nut.