You have some good ideas but that rod is pure tungsten, and for scribers you would rather use tungsten carbide. A good source for carbide rod is circuit board drills, you can buy them online but I got some twelve packs of them with a 1/8" shank and a 1/64"  drill. Their good for what they do but I have just snapped of the end then inserted them in a drill chuck then use a diamond hone to continue the taper to a point.

image property of Kyushu Sumiden

I ground a rod to a point and scribed several lines on a coarsely turned piece of 5" dia. steel and the tip didn't appear any worse for the wear. I realize this isn't extensive research but I believe for home shop purposes these rods will work just fine.

I figure with the ridges on the metal I scribed if the tungsten were too brittle it would have left a dull point…it did not, but appeared just as sharp to my finger as before I scribed the lines. So I say IMHO if you want to make a scribe of this welding electrode you'll get to draw many a line on your steel before you have to resharpen it. 

Nothing ventured,,nothing gained .

However I would still like any technical data by someone in the know just for curiosities sake and would also like to know what the 3% thoriated means ??? 

There is no need to apologies Chris, I sorry if I have been at all insulting my self.  As I said before it's a great idea to use welding rods for other purposes however they are not suitable for cutting tools, this is because tungsten has about the same hardness as tool steel but more expensive. The difference between tungsten and tungsten carbide is like the difference between steel and carbon steel with a few differences. Starting with steel, adding carbon increases hardness or rather gives it the potential to become hardened, it also sightly increases the melting point and subsequently the softening point, and also has little effect on the density. As for tungsten adding carbon increases the hardness as expected but also decreases the density significantly by twenty percent and slightly decreases the melting point. Although pure tungsten has no practical use in cutting tool it still has its place in high temperature conditions such as welding. The method I mentioned above, I have doing for years, These dozen packs cost only $7 at my local electronics store. I had bought the carbide scriber as seen below and when the tip brook off I had replaced it with sharpened carbide drill instead of buying a new scriber or spending an eternity to get it sharp. It doesn't take long to sharpen it down to a point and will be excellent for your odd ledge caliper, but since you have already made a scriber from the welding rod there is nothing with proceeding.      

Image is property of grizzly