harveyp6 said:It's a 5/16" fine thread. My initial thoughts were UNF, but comparing the drag pin to a 5/16 UNF bolt, they're close, but I don't think they're the same, so maybe it's a BSF they've thrown in there just to confuse matters.
mrtask said:5/16" UNF it was indeed. Thank you for your invaluable help Harvey. Thanks too to Netty from Mini Manufaktur who kindly lent me the right tap today. Nice bloke, excellent workshop-come-museum devoted to proper Minis, none of these hideous modern things.