Hi guys,
I feel excercised to add my two pence worth, I served my apprenticeship in the foundry industry many years ago, One of the materials we made castings for various industries for was Aluminium, Some of it was to aircraft specification, However saying that & thinking of my experiences of all those 54 years back, a couple of years before that i was on cast-iron work, before being switched over to brass , bronzes &light alloy work, making components at home as distinct from ones nicely set up in a more proffessional industrial sphere is a different ball game
Nowadays i do not know what the modern metal specifications are especially over the pond in the U.S. or Canada, & i guess i am too old to start learning now, but taking some simple rules from my ex industrial days , When, i want to make up a component in my backyard facility at home, The things i turn out, are the occasional jig or fixture to make life easy, backplates, brackets, pulleys etc
When i worked in the metal casting game one of the metals we used to get landed with on the rare occasion was on the old British metal specification LM1 (L.M. meant light metal-- Brilliant aint it!) this was an almost pure metal in fact from memory 99% i believe , It could if you were not careful lead to great voids in the casting ,shrinkages &other problems, So therefore bigger feeding heads were the name of the game
A better metal was LM 4 formerly DTD 424 This basically was a metal with a good percentage of silicon in its make up, by and large it was a metal which poured pretty easily with not a great deal of feeder head problems , A higher spec. metal was L.M.6 which was a metal of higher tensile strength etc
O.K. guys, where does this lead to with you folks? I assume you are only making the occasional little widget in your back yard for your model engine,workshop use etc Should you be making things for industry , aircraft etc, back off guys, unless you have a lot of metallurgical knowledge & know what you are about, otherwise you are in a real minefied!
So therefore making things for fun, myself & nobody else where i cannot be screwed up by litigation etc, backyard foundry work can be fun, and gives another dimension to Hobby Machining , Athough safety first is the name of the game Keep that upermost in your psyche, Hot metal is unforgiving stuff, especially when mixed with water.
Right guys raw materials___ scrap cans are by and large a pain in the butt due to impurities, a pile like a mountain for very little return for your effort, & always the danger of horsing a can into the melting pot with some liquid in the bottom (not advisable) What do i use ? Luckily i have a friendly scrap dealer who sells me suitable pieces of scrap alum, at a reasonable price Motor car pistons, are ideal , other scrap cast stuff is fine, i also tend to mix in my pot a fair %centage of extruded scrap, aluminium angle, beading etc , The pot i use gives me a max of 15lbs. of molten metal
A pitfall for home workers, is heating the metal up till it is screaming hot, thus causing oxidation a burning, What i tend to do is gently melt till the metal looks like a mirror, after skimming off the slag, then give some extra heat till the metal is a light pink, Just above the silvery mirror stage, this gives me a metal capable of flowing in the mould to 1/8" section Over here in the U.K, we unfortunately have seen the closure of a sand quarry which gave us a nice greensand, called Mansfield Red now a lot of firms & amatuers are going down the road of making up a Bentonite based synthetic mixture
Should care be taken, i find on most of my hobby stuff , i can melt a good clean melt without degassing procedures, -- remember with Aluminium you cannot de-oxidise, Only degas, In aluminium, Oxide is always present, it may be a miniscule level ,but always there, You may do as industry does, Which is, reduce it, till it is so minimal as to be of no problem
The home craftsman cannot hope to emulate the industrial folks who can afford to vacuum melt, nitrogen degass etc.
One of the biggest problem for the home guys is working out your running &riser systems + cleanliness in your mould, no breaks debris or loose parts to break off Practice, & experimentation That is the key to success.
