| Gallery, Projects and General > How do I?? |
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| Pete W.:
Hi there, all, Is it OK to straighten this casting cold or should it be heated/warmed-up? It would be a shame to crack it. On the other hand, once straightened, you'd want it to stay straight! I suppose that in industry the foundry would know fairly exactly what alloy they'd used but if Norman has cast this item himself in the backyard, the alloy composition might not be so well known. I've never seen any comments about machining aluminium alloys releasing stresses and causing warping like it often does in steel or cast iron - has any reader experienced it? |
| awemawson:
Norman, post me a chunk of the sprue and I'll run an analysis on my Analloy Alloy Analyser if you like |
| NormanV:
Stig, thank you for your offer, 75 miles, probably a bit too far. Pete, I hadn't thought about it cracking, I sawed half way through the sprue and then gave it a tap with a hammer. That knocked it off easily! It seemed too easy to me. The alloy is a mixture of car wheels and gearbox casings. It would be interesting to see what the alloy is Andrew, I will post you a piece. I am melting some more at the moment for my next casting, fortunately this one is not so critical. I'll post a picture when it is done. Thanks everybody. Norman |
| awemawson:
The car wheels at least would have been heat treated - probably 'solution treated', not so sure about the gear boxes - probably not I suspect. I'll warn the post man :) |
| NormanV:
I've just taken the second casting out of the mould, this one was slightly smaller than the previous one, 10 lbs. It was an interesting one to cast, I used one of Dave Gingery's ideas to save machining and cast it with a steel tube to form the seating for the same tube on the finished item. I blackened the tube with soot from a candle and it released quite easily with a little persuasion from a club hammer. MDF is not a good material for the flask. as I was removing the sand it fell apart due to the heat and moisture. I suppose it did the job it was only intended for a once only cast. There is a large shrink cavity in the bottom of it but that does not affect it at all. All in all I am very pleased. I have to go to buy a new angle grinder so that I can fettle the castings, my old one burnt out yesterday. Cheap rubbish! |
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