One thing I do it peen the end of the rod first and place the collor on it before I push it through the scales. I don't use the nails as I haven't found any yet... I use the 1/16" brass rod I got at DJ's hobby, they got them in finnaly

If you are good with tools you can get away with a medium soup spoon as a hammer for peening I've done 4 sets of scales now with that same spoon hehe