Whether you prefer to glue the pieces together or desire snap-fit snugness, you may need to make some minor adjustments to get that perfect fit that you're looking for. My preferred method for doing this is using 'X/Y Contour Compensation' / 'Horizontal Expansion', depending on your slicer. This setting allows you to increase or decrease the width of a model along the X and Y axes by a given amount. Entering a positive value will thicken the model, while a negative value will shrink it inward. As an example specific to this design: if the slotted driver tip is slightly loose, simply increase the width of the model by entering the desired amount of growth (i.e. [0.1mm]) and print a new, better fitting one.