Hi, I've a windsurfer brand sailboard with a brass coloured nut inbedded flush with the deck, between the mast step and centerboard case. Could someone kindly assist in informing me of the thread size of that nut.
I've failed with metric 4mm (too thin), 5mm (too thick) and 3/16th (just didn't fit).
Your assistance would be appreciated.
NB being a longish board it is not convient for me to transport it to a shop that sells fastenings in order to seek their help, if they are willing and able, in testing their stock.
6mm or 8mm or the stuff is crossthreaded 
tap that sh1z 
windsurfer "brand" never used standard thread or any thread at all. lots of copies had "windsurfer" stickers on them.
Hi, I found it by trial and narrowing down the field. The answer being a 3/16th inch diameter thread but 32 threads per inch, in size chart its "No. 10, 32 UNF". NB 1/2 inch appears correct lenght, for that board. An original "windsurfer" brand, built mid production era, before what appears to have a screw in centre board case and mast step. Thanks for reading, the replies and enjoy your sailing.
Mmmhhh, Windsurfer did use standard (english) threads, except for the screw-in mast piece that came later in 1985.
Anyways, what do you want to use this screw hole for? Again, never ever seen someone use the little screw on those pre-1983 boards...
