Steering wheel boss

[Stevo302]

Ever since I have had the car I have had problems with the boss not fitting right. The horn never seems to work correctly either. The horn used to be a switch on the dashboard. Now I am trying to get it to work from the centre steering button.
When the boss is fully tight there is hardly any room between the boss and the horn disk that is fitted into the steering colum. When I turn the steering wheel sometimes the horn sounds so it's not that great.
Any ideas to how it should all be fitted?
Regards.

[Stevo302]

Thanks for the help. I've sent the boss off to get skimmed on a lathe and take things from there.
Regards.