I am currently importing images from a number of different catalogs and when doing so Lightroom is creating smart previews and 1-1 previews, which is exactly what I want!
As soon as the images are imported I have been filtering the JPEGs and deleting them as I only want Raws. However, as the previews are still being built it says that some smart previews can't be built, which is not a problem, I just hit the button in the top and it finishes what I stopped it from doing when I deleted the jpegs.
I have noticed that the 1-1 previews carry on and I was just wondering if LR knows to delete the previews for the JPEGs after it has finished or are they still sitting around unable to be deleted.
If i've not explained myself properly please do say and I'll try a bit better