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Almost certainly a violation of copyright, and whoever uploaded it, and everyone who downloads and uses it are potentially subject to prosecution. (The most likely one to be prosecuted would be whoever uploaded it -- if he can be identified.)
I can't have a try, because I don't receive any alt.binaries.* newsgroups on my news server (by choice).
Since there is no advertising in _Machinery's Handbook_, they depend on sales for all of their income. If everybody downloaded this one, and didn't buy a copy, they would go out of business, and you would have no such resources available.
I don't object to scanning and posting (on a web page) of things long out of copyright, and unlikely to be re-published (e.g. Rose's two-volume _Modern Machine Shop Practice_, but things still in copyright, and still in publication are a different matter.
Enjoy, DoN.