About the (many) live center types?

[Mitch Alsup]

The bull nose live center if for things where you can't put a center in (like tubing, pipes,...) but you still need to turn the outside all the way to the end.

The extended nose live center is to allow access to the far end of the outside turning part where a straight 60º cone would interfere with the tool. These come in vairous nose sizes.