I picked up a 1976 schwinn that I am restoring and I have come to a problem. The headset. I have determined that the headtube is 21.1mm, however before I determined this I bought a 1 inch threadless fork. Is there any way of combining the two? I know that 21.1 is still used in bmx bikes, so I thought is ask here. Thanks for any help.

The headtube itself measures 21.1mm? i think that size maybe a schwinn thing.

I think you maybe refering to the fork tube dia? thats all i can think of at that point i don't know why you say anything about a 1"threadless fork. Take a picture or something, but i kinda think you may have it backwards