3.1.4 Assembly Tolerancing Another part of the equationis the assembly variation defined by the letter ‘‘P.’’This variation represents the location of the component inrelation to its true position as defined by the design. Theterm diameter of true position (DTP) is used to describethis variation and is a single number that can be used in thedimensional tolerance analysis.As an example, for establishing the target heel protrusiondimensions of the example shown in Figure 3-3, the followingconditions would be true:Where:J is 0.5 mm (target heel fillet).C is Stol (RMS) = 1.29 mm (see previous calculationsfrom component dimensions).F is 0.1 mm (assumed fabrication tolerance).P is 0.05 mm (assumed assembly equipment placementtolerance).