^ A MAC model SC30 is a special ball joint socket, so the assignment of a part number can be anybody's guess.
MAC SC30 ball joint socket (photo: ebay)
Generally speaking, most American tool manufacturers followed a fairly standard convention when assigning part numbers to SAE sockets - in
many cases what you will see is the
size of the socket incorporated into the
part number by 32nds of an inch.
(e.g., Duro/Indestro 1220 socket = 1/2" drive x 20/32" - or 5/8")(e.g., EASCO 51-1114 - 1/4" drive x 14/32" - or 7/16")
Not all manufacturers followed this convention - some of them make no sense at all.
When you get into 3/4" and one-inch drive stuff, the "rules" appear to go out the window. (see list of sockets below) (although if you look closely at the list below you can see the "32nds" part in many of the part numbers... some of them make sense, others not so much.)
