Home enthusiasts discuss their Foundry & Casting work.
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Gentlemen, I am thinking of turning a steel hub and knurling it, and casting aluminum with the steel hub left in it. I know that aluminum shrinks more than steel, so I am wondering if this practice is workable. This would be about a 3" diameter hub with the outside diameter of the casting being about 4.5", and about 3" long, feedback would be appreciated. I am conspiring to make a aluminum cog belt pulley, that does not rust and eat belts. thanks
BY my back-of-the-head calculations you should end up with *roughly* .006" interference if you fully pre-heat the steel. Should work, but check my numbers. The risk is cracking the aluminum.
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It will work just fine, Dave Gingery used the technique extensively in his workshop book series. If you never want the cog to slip on the shaft, either rough up the mating surface of the shaft, or better yet cut or file a couple of flats on the shaft. The aluminum will conform to the cuts, and you will rip the end of the shaft off before it will slip.
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus
I have an engine block out in the shop, about 3-1/2" bore, that was die cast aluminum over iron liners. The liners have wavy ridges on the outsides so they can't shift if the engine overheats.