Thanks very much LADS for all your comments .
I no that i may only use these cone centres a few times a year ,but when needed they are very handy (i just like making tools ) and others may not wish to go to the time to make them , This is what i used in the past ,very quick and fits on standard centre
Normal revolving centre
Drill a hole in a lump of stock say 12mm this is so you don't have to bore to a piont, then bore a 30 deg tapper ,to mach the centre
Spin it around and ruff turn the outer tapper what ever you fancy
Then stick a piece of bar in the chuck and face the end
Next fold a small piece of emery paper grit on the out side and mount the cone on the centre ,place emery paper between cone and bar in the chuch and lock up tight
Then using light cuts finish turn the cone
Used this one for years
Regards Rob