Azfar Mahmood, a senior piping designer, shares a tip about controlling the size of the crosshairs in AutoCAD.
"The CursorSize system variable, when set to 100, will show the crosshairs fully across the screen. This works fine on the standard snap style, but on isometric style the cursor size does not fit the full length of the drawing editor or your screen. A workaround solution is to set CursorSize to 99% instead of 100%; you will find the crosshair fits the full length of your screen."
Notes from Cadalyst Tip Patrol: I couldn't repeat this occurrence in AutoCAD 2011 or 2012, but the tipster reported it happening in AutoCAD 2008. I can't test it in that version as I do not have access to AutoCAD 2008.
Regardless, to control the size (the length) of your AutoCAD crosshairs, you should use the CursorSize system variable. It has a value between 1 and 100. These values are not absolute lengths, but rather percentages of your screen. A setting of 100 draws the crosshairs across 100% of your screen, a setting of 50 draws them across half of the distance of your screen, and so on.
There are two snap modes for your crosshairs: Rectangular and Isometric. The standard format is rectangular: your crosshairs are horizontal and vertical. In Isometric mode, your crosshairs are in one of the three isometric planes; press F5 to toggle the planes. Use this mode when you create isometric drawings, piping and instrumentation diagrams, etc. Type OS on the Command line and activate the Snap and Grid tab.