With the right stock on hand, I happily turned down the aluminium block to close to the required dimension and slowing turning bit by bit till it fits the recess at the back of the 4 jaw chuck. After playing with steel for a while, I find cutting aluminium fast and easy. The job was quickly completed.
The half done ER32 collet chuck was remounted on the 3 jaw chuck to clean off the remaining skin and the back faced. I'm now ready to turn the recess.
The experience gained while turning the nose helps. I'm starting to get some feel of spindle speed, depth of cut, and rate of feeding. Good that I'm feeling more confident in use the lathe.
The next challenge would be the recess, cutting the threads, and boring the taper. I'll be taking it slowing to gain more understanding of the process.