how to you make a hallow 3in tall cylinder with about 1/5in thick?

Answer 1

Extrusion or rolling. For a regular shape like a cylinder, rolling is more likely. You need to start with a solid rod, which is then put through a rolling machine that has internal and external rollers. The operation will be conducted at high temperature and high pressure, which makes the metal more malleable.

Answer 2

Here's my list.

1) Lathe. Drill out from solid rod.
2) Automatic screw machine. Same as above.
3) Continuous casting.
4) Centifugal casting.
5) Extrusion.
6) Pipe welding.
7) Many others.

Answer 3

How many do you need made? What is the tolerance?High tolerance and if it's only a few you would do it on a lathe.