Join our CAD community forums where over 25,000 users interact to solve day to day problems and share ideas. We encourage you to visit, invite you to participate and look forward to your input and opinions. Acrobat 3D, AutoCAD, Catia, Inventor, IronCAD, Creo, Pro/ENGINEER, Solid Edge, SolidWorks, and others.
Did you use the "thread" feature tool to thread your holes or did you make threaded holes using the "hole" tool? There is a big difference between the two.
If you "threaded" your holes (meaning you have one feature in your model tree for either an extrude or hole and then another feature to thread) you will not be able to mirror your threads. Threaded holes (meaning you have ONE hole featurein your model tree) can be mirrored and your threads should come with them.
Within the mirror feature there will be an expanded selection, there will be a creation method option to be either identical or adjust to model. With identical, threads don't appear to mirror, however with adjust to model they do. Within idw the mirrored thread is displayed but will not be recognized.