20.6 mm socket

[supersteve]

I see some 20.6 mm sockets in Granco's catalog here, fourth page:
http://grancoind.co/catalog/halfinchdrive.pdf
A Google search led me back here to some discussions on this board where some folks suggested it was a metricified 13/16" socket for spark plugs.

That seems strange to me since Granco already catalogs a different part number for 13/16" sockets. What really puzzles me is that they have this size in a shallow socket too, so I suppose that rules out spark plug use for that one.

?????????

 

[therealwormey]

they make that for those OCD people thats gotta have every size for ever peg

 

[snapmom]

Snap on made one too. Plug sock.

 

[mailpup]

13/16" was also a common lug nut size on domestic cars. These days people most likely just use a 21mm if they don't have a 13/16" socket but back in the day, IMO, the same thinking went into making the 20.6mm socket for lug nuts as it did for the 13/16" spark plug socket. The 13/16" size was probably singled out because it was so commonly used on lug nuts and lug nuts were an item frequently removed and reinstalled.