I know right.Wow Lin, 6 inch is pretty big. The biggest I can find is 3 1/2 inch. https://www.toolpost.co.uk/product/bull-nose-cone-live-centre
"DARN IT"I think you may have to make it yourself on your metal lathe. If I still lived and worked on the coast I could have snagged some 4" or 6" thick aluminium scrap but no more.