Notes

Pad and Via size:  One should maintain the largest practical annular ring to insure a good mechanical, as well as electrical and thermal connection.  There is a wide variety of pad sizes and shapes available to accomplish this.  Octagonal pads are far superior to round.

Eddy's rule:  the pad or via size should be 50% greater in diameter than the diameter of the hole.

Eddy's Inverse:  the hole should be 2/3 the diameter of the pad.

Plating through and tolerances: Hole sizes should be specified as finished hole sizes.  This compensates for the loss of diameter in plating through the hole; the hole will be around .002" smaller than drilled.  This figure represents an average that can vary by as much as 30%.  Larger holes will take more plating than small ones as a rule and holes near the outside of a panel will also take more copper.  On the other side of the equation, the plating thickness will be greater than the .002" decrease in hole diameter. Due to etch-back and internal stress, you may have as much as .002" copper thickness.  This thickness on both sides of the hole adds up to .004" total copper, yet the hole is only .002" smaller.

Obviously, one needs to be careful in considering hole sizes, as there are a great many variables including accuracy of hole location and tolerances within the component to be placed.

A good practice is to allow .005" extra hole diameter to accommodate all of these variables.  This also allows de-soldering of defective parts during repair.