What is the proper way to adjust clearance?

[jwlister]

I am using FDM 3D printing to print nuts and bolts. Sometimes, the bolts do not fit into their corresponding nuts. Is there a way to adjust clearance to match the accuracy of my 3D printer?

Let's say I am printing a cylinder and a tube, where the cylinder is meant to slide into the tube. If I print my cylinder and tube, and the cylinder does not fit into the tube, then I would simply decrease the diameter of the cylinder by some small amount, then try again. Rinse and repeat until I get just the right fit I am looking for. But how can I do this with threadlib? Correct me if I'm wrong, but I don't think scale would be the correct approach here, would it? Scaling a bolt so that it fits properly into its corresponding nut seems like a ham-fisted approach that would not maintain the proper fit of the threads (but maybe I'm wrong; I honestly don't know).

This issue is closely related, but the discussion there seems to be about whether threadlib was generating incorrect threads. Just to be clear: there is nothing wrong with the nuts and bolts that threadlib generates. The fact that they sometimes do not fit is indeed a production issue. However, different production methods have different levels of accuracy, so it is not uncommon to adjust the models being produced in order to account for these variances in accuracy. The question is, how is this properly done in threadlib? Or, if threadlib does not offer any specific facilities designed to adjust clearance, then what is the recommended way, in general, to "manually" add clearance to threads?