Chapter 3 Datums 115 The Meaning Secondary datum feature B Adjustable location Primary datum feature A Tertiary datum feature C Datum feature simulator of datum feature B Expanding cylinder perpendicular to datum plane A Datum feature simulator of datum feature A Datum axis B Datum plane A Datum axis C Datum reference frame Datum feature simulator of datum feature C Expanding cylinder perpendicular to datum plane A Location distance adjustable from datum axis B Example 3-43. (Continued)