Hot answers tagged hub
If it screws on then it is a freewheel not a cassette. They are not the same. There is a link in my comment. Your spacer kit with one sprocket was probably for cassette / freehub. It is not going to work. I suspect you can find a freewheel single speed conversion. You need a single speed freewheel - not a sprocket and a lockring.
Only top voted, non community-wiki answers of a minimum length are eligible