For playing around at a DIY level when you are the person who is going to suffer the consequences that is okay. But it is a different thing when the word 'manufacturing' is mentioned because that implies selling to a third party. Backyard cast aluminum of undefined composition from scrap is rarely adequate and can be downright dangerous. The 'billet mystique' I mentioned does have validity and it has grown out of the market for adapters and accessories in the modified motorcycle and offroad 4x4 market. Amateur cast aluminum does not cut it when you are making transmission adapters or fancy footpegs; giving the impression that maybe it can is not entirely responsible.