tolerances for mating parts?

Hello, can any one help me figure out the tolerances for some parts that assemble and disassemble when put together? The material that i'm using is polypropylene as the shell has living hinges and Mattel joints. I have triangles that assemble over the shell that have cylindrical pins that fit into hexagonal Mattel joints. The pins have a radius of 2.3 mm and the hex joints have a radius of 2.2238 which is 0.003 smaller than the pins in order to engage properly. However, I realized that I also have to consider tolerances to allow for shrinking and expansion of the plastic during manufacturing. Does anyone have any idea or guidance on how to calculate the proper radius tolerance for both the pins and Mattel joins before I order the molds?