Sapim CX-Ray spokes.

Recently a spoke in the front wheel of my Flashpoint 60 carbon
wheelset broke in two near the hub were it crossed another spoke.

So, I ordered some replacement Sapim CX-Ray bladed spokes from
Wheelbuilders.com. I ordered five of three different length spokes
as the front wheel uses one length both sides but the back wheel
uses different (and slightly shorter) lengths depending upon drive
or non drive side I guess because of the way the wheel is dished.

The spokes arrived and I threaded the original spoke nipple onto
the threaded end of the old broken spoke upside-down so I could
pass the nipple through the hole in the aluminum rim and out to the
hole in the carbon wheel a distance of a 60mm. My plan was to
then thread the nipple onto the replacement spoke and off the old
broken spoke I was using to guide the nipple.

But, alas, the nipple wouldn't thread onto the new spoke more than
about a turn before it commenced to bind up. Well, it turns out there
are two commonly used spokes and spoke nipples 5 gauge and
6 gauge. It appears that the original Sapim spokes are 6 gauge while
the replacement Sapim spokes are 5 gauge. So I had to order some
5 gauge nipples from Wheelbuilders.com. They arrived via FedEx
yesterday and using the new nipple and the new spoke they threaded
together easily. So, I trued the wheel back up and am ready to go.

So what's five gauge and six gauge mean? Is it a measure of thread
diameter or thread pitch? With the naked eye I can't see a difference
at all so it's very minor. And, why don't they mark spokes with a 5 or a
6 so one wouldn't have to guess what nipple to use?

--
Sir Gregory