Center between two holes
On more than one occasion, I've watched someone trying to measure the center between two holes by eyeballing the empty space and guessing the exact center. The other day this happened again (He was a millimeter off when I measured it) ... sooo I've decided to go ahead and mention this for the 10% (or more) that don't know this simple fact:
THE DISTANCE BETWEEN THE CENTERS OF TWO LIKE HOLES IS THE SAME AS THE DISTANCE BETWEEN THE LIKE EDGES....
The edges are a lot easier to see and measure, so next time try measuring between the left or right edges.
Instead of doing this: Try this:
DIFFERENT DIAMETER HOLES
For things like root ribs where the two holes are often different diameters (based on the easiest things to measure):