Figure 17. Co-datums:

When two datum features of equal importance are used to establish a single datum plane or axis, they are called co-datums. Placing the appropriate datum reference letters, separated by a dash, into the datum reference compartment designates a co-datum. See Figure 17. (next)


Figure 18. Inclined datum features:

A datum feature can be at an angle other than 90 degrees with other datum features. For example, in Figure 18, the datum feature C is at an angle of 60 degrees with the datum feature A. To inspect the part, the simulated datum plane C must be at an angle 60 degrees (basic dimension) with datum simulator A, and 90 degrees with datum simulator B. The part will be placed within the datum simulator frame following 3-2-1 rule, and the location of the hole will be inspected. (Top)