Many thanks everyone!
Matt - Yes, I know aluminium (like all materials except H2
O) shrinks when it freezes... I didn't know the percentage though, thanks! Not as bad as Machinable Wax then, that's about 5% IIRC. Maybe more. SERIOUS shrinkage...
wgw - interesting idea; isn't it a bit tricky getting the two halves properly concentric though? Mind you, I like your idea because it would allow you to make a variable pitch pulley with ease... that is where the groove width can be adjusted (usually by screwing one half into or away from the other half), thus fine-tuning the ratios... definitely one to consider! Thanks!
Phil, as soon as I'm off the slow boat from
China, I'll drop you a line! Don't know when that will be yet, probably another month or two. Not sure where I'm going to put any of this stuff... the workshop looks like it's been hit by 1/2 dozen cyclones, a hurricane and a fairly severe earthquake at the moment... it's going to take a solid week of work just to get to some of the machines!
John - I've heard about dumbell weights (well, strictily speaking, weightlifting weights), wasn't the consensus these days that the metal was so poor it was positively dangerous to machine? I'm thinking of cast iron weights, I don't suppose there'd be any point making aluminium ones...
Pete - someone's selling one on Amazon. £14.50!! Now that's inflation for you.... I'll keep a lookout for a more reasonably priced example I think.
MC - I'm going to give that a go right now, thanks for the link!