Casting Aluminum tight to a steel hub

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AllenH59
Posts: 365
Joined: Wed Mar 16, 2011 1:26 pm
Location: Prince George BC Canada

Casting Aluminum tight to a steel hub

Post by AllenH59 » Thu Aug 24, 2017 9:01 pm

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

John Hasler
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Re: Casting Aluminum tight to a steel hub

Post by John Hasler » Thu Aug 24, 2017 9:21 pm

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.

AllenH59
Posts: 365
Joined: Wed Mar 16, 2011 1:26 pm
Location: Prince George BC Canada

Re: Casting Aluminum tight to a steel hub

Post by AllenH59 » Thu Aug 24, 2017 9:38 pm

I would think that if it did not crack the Aluminum it would make a never come off kind of fit..

OddDuck
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Re: Casting Aluminum tight to a steel hub

Post by OddDuck » Fri Aug 25, 2017 11:40 am

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

TRX
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Location: Central Arkansas

Re: Casting Aluminum tight to a steel hub

Post by TRX » Fri Aug 25, 2017 2:22 pm

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.

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