Jon,

To bend aluminium successfully you need to anneal the metal. Firstly rub a bar of ordinary household soap all over the area you want to bend. Use the bar of soap dry and keep rubbing until you get an even coating. Next using a small propane torch which here in the UK can be obtained from any do it yourself or hardware store, heat the coated area with the torch keeping the flame moving. Do not play the heat in one place and keep heating until the soap turns completely black. At this point stop and allow the metal to cool down completely to room temperature. You will now find that the metal will be very soft and the bend can be made with very little force. Aluminium alloys actually age harden, so if you now leave the header for several days it will eventually revert back to the hardness level it had before you annealed it. The bending process also work hardens it a little so if you need to adjust the bend once youve made it you should re-anneal using the soap indicator method.

Hope this helps.

Malcolm Harris