Originally posted by divertom
and whats half inch UNF?
It is an imperial size fine thread
1/2" is approx 12.5mm in todays money so i suspect the ones you have purchased are normal M12 s/s nuts and bolts. The fine thread simply allows more threads to be in the nut thus making it stronger. Unfortunatly no one seems to stock the 1/2" unf bolts in the length you require so you have 6 options
1. Run the M12's (I do on the bottom lift bolts on mine but i wouldn't risk it on the top bolts)
2. Buy some 1/2" UNF threaded bar and make some bolts by welding nuts onto one end of it. ( again ok ish but you don't get any land on the bolts so they are again slightly weaker.
3. Run with M14 nuts and bolts. ( i've heard of a few people doing this but haven't tried it myself.
4. Bite the bullet and purchase some genuine mercury s/s bolts with brass nuts.
5. Find someone in the states that can send you some as they are common over there.
6. Someone on this forum will see this thread and have some you can buy