The article presents a process of modelling dimensional couplings in assembly operations using single-circuit graph models that describe the mating mechanism of separate parts. The method of partial interchangeability is used, being the most common one in the current manufacturing conditions. Calculations based on the developed mathematical model are considered. The model can be applied to single-circuit and multi-circuit dimensional schemes in various manufacturing conditions. For large-scale manufacturing, an algorithm is proposed for determining the scattering field of maximum limit values of adjustment gaskets thickness. The calculation method is demonstrated on specific examples describing the maximal cases of interaction between dimensional couplings of parts at an assembly site; whereby the relative controller link is considered having a positive reduction ratio.