Brass Brass tubing is generally used for our stuffing tubes due to its strength over aluminum and copper. The stuffing tube takes quite a bit of load, especially when our boats are moving at 40+ MPH so you want something strong and rigid.  In order to bend brass tubing you need to first anneal it so it can be easily formed. The brass tubing we buy has been cold worked during the process of forming it in to a tube. We like those hardened properties cold working creates for our stuffing tubes so you only want to anneal the area you intend to bend. The picture shows the crystal structure of a cold worked brass.
Annealing is really a comprehensive term meaning many things, but it is a heat treatment process that may be used to: - Remove stresses
- Induce softness
- Alter ductility
- Change toughness
- Alter electrical magnetic, or other physical properties
- Refine the crystalline structure
- Remove gases
- Produce a definite micro-structure
 For our purposes annealing is the softening of the brass caused by recrystallization of the lattice via a heating and cooling cycle. Recrystallization will cause the formation of a new set of strain-free grains within a previously cold-worked material. This is the crystal structure of a cold worked and annealed brass, compare it to the above picture.
To anneal you first mark with a pencil the area on the tube that needs to be bent. Next take a propane torch and begin to heat that area of the tube to get it red hot. Once its hot you let it cool down at room temperature or quench it in some water. Note that quenching may harden the tubing back up some but not anywhere to its original work hardened state.  Once its cool, bend away! For very easy curves, you should able to slowly bend freehand or over a form. For tighter turns, kinks can be controlled by stuffing the annealed brass with fine salt or sand or even string trimmer string. There are also various tools available from K&S to help bend tubing.
Copper and Aluminum  Both copper and aluminum are already soft enough to bend, so what we need is a way to prevent it from kinking during the bending operation.
I found that you have to pull the tubing during the bend, you basically grab the tube farthest away from the bend and really pull on it while you bend it around the shape you want. If kinking occurs you can fill the tube with a flexible solid like salt or sand, this prevents it from collapsing during the bending but is a bit messy. I've also had success by inserting string trimmer wire in the tube and then bending. Using this technique you should cut the wire in two and insert it from both ends of the tube to ease the extraction when the bend is done. | 
