Hello John,
Maybe I am stating the obvious but you said billet so I hope you are using tailstock support and not relying on the grip in the chuck.
Some aluminium can be 'sticky' try using paraffin or WD40 as a cutting lubricant, it will assist in getting a turned finish. HSS is better suited to aluminium but is must be sharp
Don't cut with too deep a feed, that will just induce chatter, and try varying the turning speed to find something the lathe likes so that you produce turnings.
Regards Brian [I have a few more miles on the clock than you, but what does that count ! ]
I don't suppose I have covered all bases, but from similar problems made on the forum before these things are the ones that have most beneficial effect.