I read a few posts about concerns regarding threading the soft material that MDF is made of. Different folks had different ideas that all made sense, but I didn't see this suggestion. Modelers strengthen balso wood fo threading by putting a few drops of super glue down a threaded hole, then rethreading the expanded wood once the glue has dried. I've used the trick a few times myself so decided to try it on a JGRO I've been building. Talk about NICE!
The threaded holes have sharply defined threads and the threads hold very well. I can thighten the screws to a mild to mid GRRRR and the threads hold and parts are held together very firmly. The bottle cost $8.60 at my Hobby shop and probably much cheap at a place like Tower Hobbies on line. It was enough to do all of the threaded holes wth aboout 1/3 left, and I'm very happy with the results.