Bolt and thread size that comes with replacement letterbox

[rarara]

I am trying to determine the bolt size on something I am modifying as I need to buy additional nuts but other than it being I think M6 and 1.5mm pitch I am struggling. The only thing I know for sure when looking through my box of spares for a match is that it is the same as the lengths of threaded bar that you get in replacement letterboxes.

Anyone know the exact gauge of this bar? If I determine that it should make searching online a lot easier.

 

[Burnerman]

Traditionally, the thread was BSW.....British Standard Whitworth.
John

 

[scbk]

Go to a local nut and bolt shop - they should tell you what you have and be able to sell you the nuts to match

 

[mattylad]

take the thing your modifying with you.