[go4gold]

The stuff from your lhs is probably junk not cheap just junk. You can find tap extractors at mcmaster carr along with relativly inexpensive taps. Most broken taps are from the hole being to small, the tap not started straight, or any bit of side load especially on small taps. If you have a drill press you can use that to help keep the pressure straight down without any side force. If you really need to keep the original piece of metal there are companies that do broken tap and drill removal without damage to the hole. i think most of them use a process called EDM. Mcmaster also has angle aluminumwith 3" walls and 1/4 "thick. I could not find any 5mm thick angle. Here is a part # to look at 8982K62. This tap is Nitride treated(for aluminum and other soft metals) 27175A512 It's 10.52. Not cheap but will last This one is uncoated for 5.83 8305A32