A five degree-of-freedom compliant parts mating machine, or PMM, is described. The PMM is capable of analyzing three dimensional assembly processes, regardless of part shape. It measures forces and moments during assembly and also records the linear displacement and rotation of the parts being assembled. The effects of positional errors, angular errors, ratio of rotary-to-linear stiffness, and the location of the center of rotation on maximum insertion forces during assembly are described. Experimental results for the three dimensional assembly of a compliantly supported peg-and-hole are presented.