3104 alloy is pretty weak. The lids and tabs a 5182 which is a bit stonger but you’d be better off taking an old aluminum baseball bat or bike frame and using that metal.
You are probably quite right...it probably won't keep a sharp edge, and will probably snap easily, but it could do some damage to someone stabbed with it. I like the video as an example of creative use of commonly found objects. The sand casting method may be a way of crafting other useful objects. The same method may be used for crafting brass alloy objects.
I don't know how to post videos,, but I saw one a while back , they took plastic soda bottles,, cut it up in little pieces ,, put them on a paper plate , about 2-3 inches wide 8-10 inches long,,then microwaved them till they melted together,, then cut , formed and sharpened into a pretty sturdy looking knife. Soon as I get another microwave,, I'm gonna give it a try.
Depends on the source of the videos...You Tube and Vimeo videos should be straight forward...@sec_monkey should be able to elaborate on that .
