According to J. C. Harrington's initial studies, the time periods and average bore diameters are as follows (Deetz 1996:28):


Diameter       Dates
 
9/64           1590-1620
8/64            1620-1650
7/64            1650-1680
6/64            1680-1720
5/64            1720-1750
4/64            1750-1800