Thanks guys!
my bar is 180cm, about 2cm diameter (1 inch). I calculated the 9kg based on these measurements (plus a bit for the knobs) and the density of iron.
However, when I work out the weight by weighing myself carrying, or not carrying, the bar, on my (fairly dodgy) scales, it comes out at around 7.4kg (average over several measurements).
Anyway, it still means that I have hit a bench of 120kg, which was the goal I set myself about three years ago, when I read somewhere that a "Man" should be able to bench one and a half times his body weight.
Then, I was just under 80kg - now, I'm around 86kg, so I still have a bit further to go ...
@Timeah - thanks, but I've got all the weight plates I need for my level at the moment.