Bolt size vs Wrench size??

there isn't a set amount for metrics just as there is no set amount for SAE fasteners take a 1/2" bolt for example... the common head size is 3/4", however, an ASTM A325 (heavy hex grade 5) 1/2" bolt has a

7/8" head. there are also tight clearance 1/2" bolts that have a 12pt 5/8" head.

I've got 10 MM 9.8 fasteners with heads from 14-17 mm in size... depending on where I got them from.

-Bret

Actually there is no standard for the head flats in relation to the thread diameter. Here is a small section from the "Machinery Hand Book".

Metric Threads

8mm bolt = 13mm flats - difference 5mm 10mm bolt = 17mm flats - difference 7mm 12mm bolt = 19mm flats - difference 7mm 14mm bolt = 22mm flats - difference 8mm 16mm bolt = 24mm flats - difference 8mm

United National Threads

1/4" bolt = 3/8" flats - difference 1/8" 5/16" bolt = 1/2" flats - difference 3/16" 3/8" bolt = 9/16" flats - difference 3/16" 7/16" bolt = 5/8" flats - difference 3/16" 9/16" bolt = 7/8" flats - difference 5/16"

nospam