How precise do you need to be? Accuracy with edge finders varies depending on the type of edge finder (mechanical/electronic) and the method employed (run-off/light line).
Or are you refering to the conductive electronic variety (meaning you must be working with metals) which can be out if the surface isn't scrupulously clean.
If you can live with .1mm error just use a dowel in the chuck and a piece of shim to set with.
For supreme accuracy I always use a DTI.