19-04-2016, 03:08 PM
Using that Table 
I have an old Whit/BS spanner that is a good fit on drain plugs so I guess it must be 7/16 W; 1/2 BSF.
I only use it if some previous chimp has gorilla'd it on

I have an old Whit/BS spanner that is a good fit on drain plugs so I guess it must be 7/16 W; 1/2 BSF.
I only use it if some previous chimp has gorilla'd it on
