IPC-2222 - Sectional Design Standard For Printed Board For Organic Printed Boards, Table 9-3 � Plated Through Hole Diameter To Lead Diameter Relationships will give you the standard information you require.
If we can�t get proper hole fill after trying all the suggestions found after searching the fine SMTnet Archives, we figure the designer blanked the pooch. Practically, if the finished hole diameter of the bare board isn�t 10 thou [0.25mm] larger than the finished lead diameter, you�re going to have trouble somewhere in the process.
Hole fill is a major process indicator. But as you'll find, there are instances [ie, thick boards, cracked hole plating, etc] other than clearance when holes will not fill.
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