From my second cast, I produced the following two blobs. The left hand one was much better than previous attempts with a large section of straight sides and a better finish. I expect the right one would have been better if it was a deeper casting and had I not run out of metal for it.
These were hacksawed and filed into rough blocks ready for machining. A little like a famous meal with loaves and fishes, I keep ending up with enough offcuts to provide as starter material for the next melt. Obviously as I get better at preparing the molds this will reduce, as long as I’m melting some large blocks (such as the disk drive casings) then this should not be an issue.
Before I can continue with the larger block, I need to make up some suitable clamps or faceplate dogs so that I can attach them to a faceplate. This block is too large to be held in the chuck. The book Workholding in the Lathe (Workshop Practice Series) has given me some ideas on how to make these, I’m planning to make the faceplate dogs out of hexagonal steel rod with M5 clamping screws.