problems with cragar SS lug nuts???

I just got some cragar SS 5x4 for my stock duster with 7/16 LH 20 lug nuts that summit states go with those wheels. But for some reason they dont fit i cant get the to screw on there, the old ones are 7/16 and go on there just fine but the cragar ones its like they are too small and arent wide enough to fit on the stud. Anyone ever have this problem?? the guy at the tire place said that the 20 might be why it was too small but i had 20 on there before he said i may need a 21 or 22 cause the hole is wider. I just dont understand why they dont fit if they are the same size as the old ones as well.