Another almost forgotten way to locate the exact centerline height is to use a thread center gage but it will only work with cutters having the point on the same plane as the top of the tooling such as HSS that has not had a rake grind to it you place the large V notch against the stock in in the chuck and align the point of the cutter with the center of the notch while aligning the pointed end of the gage with the top edge of the HSS.
Most machinist have one of these tools tucked away in their tool box and hardly ever use them anymore I use mine mostly when I have to grind a piece of HSS into a threading tool
Click image for larger version.  Name: 2ZVD9_AS02.jpg  Views: 129  Size: 57.6 KB  ID: 42210