Hi !
I live in France (so please pardon my English).
I've had through some family members an old steam machine. Though some pieces are missing or broken, I did manage to run it a few years ago.
But I want to give its orignial beauty and completion, so then I can start trying to make my own live steam engine 
My problem : most of my measuring tools are in metric, but bolts etc seem to be in inches.
Here are my measures :
1/ Tubes thread : 3.4mm diameter, 40 – 0.635 for the thread (I got a thread reader in inches !)
2/ Bolts for cylinder fixation : 2.78mm, 48 – 0.529
3/ Support for water level : 5.96mm, 30 – 0.846
4/ Water Tube thread : 7.84mm, 30 – 0.846
So from this table ( http://www.allcap.co.uk/Conversi.htm ) I guess 4/ is something between 4BA and 2BA – 30, 3/ is 5BA – 30, 1/ is around 10BA – 40 and 2/ around 12BA – 48 ?
Or are those unusual and could be in metric/other system ? (doesn't makes much sense considering the values)
I'll try uploading pictures of the machine when I'll get the PC-phone connection working ^^'
Thanks !
Best regards,
Thomas.