Finding the appropriate size is rarely a problem, Finding a spanner or socket often is,
I needed a 1.6mm spanner or socket to drive some nuts and bolts,
Riffling through my box of things that will come in handy one day, Staring me in the face was a Hex headed screw,
The size of the thread was unimportant, what was, was what size hex driver fitted into the head?
1.6mm


So turn the screw upside down and fit the head of the screw over the 1.6mm bolt or nut and turn until tight.
Just one question,
Why do people make particular size nuts and bolts if nobody makes the spanners and sockets to drive them?
Shaun.