The spacing between letters is one of those things that you never notice if it's perfect, but will infuriate you if it's wrong. This XCKD comic further illustrates:
On a computer, it's easy to line letters up properly. But if you want to 3D carve some loose letters and make a wooden sign that will last the ages, it's a bit more difficult.
Luckily, David Picciuto aka The Drunken Woodworker has come to the rescue. In this project, David explains a simple technique that allows you to line up lettering perfectly, every single time. Want to know the secret? Check out the project page and be enlightened (and properly aligned).