Originally Posted by
thesuper
Scooper, you've assumed that because a spoke has about 10mm of threads than the nipple does as well.
the most common nipples are 12 mm long. so they can't have 10-12mm of threaded portion.
the common 12mm nipple has no thread on the flat portion. the only part that threaded is the round part before the head....and a one or two at the head.
Arrghhh!
OK, round up if you must and suffer the consequences.

I give up! Uncle!
From Musson
Wheelbuilding: