There are several books that are essential for a machinist to have in his library, foremost among these is "Machinery's Handbook." The MH contains an incredible amount of information, and the book's sections on threading, taps, dies, drills, etc are worth the price all by themselves.

http://new.industrialpress.com/machineryhandbook

You don't need to buy a new copy. The information you need is available in any of the editions from about the 20th edition forward. What changes every few years from about the 25th edition to now is more modern machining stuff, 3D printing, EDM metalworking, etc. For someone seeking to have access to the most commonly used machinist material, a 25th edition would work fine.

Now, how to run a lathe:

http://www.vintagemachinery.org/pubs/1617/3789.pdf

This is a book by South Bend from 1914. I'm pointing to the older edition, since they had so much more information about grinding HSS tooling back then. Most people (including me) will tell you that modern machinists barely use HSS tooling any more, and they're right. Inserted carbide tooling is probably the single biggest return on investment any machine shop can make. I use inserted carbide tooling - but I still grind and use lots of HSS tooling as well. The early "how to run a lathe" books also cover lots of mechanic's operations on a lathe, which makes it useful for farmers/truckers/etc.

Threads: I could write a whole dissertation on threads here, but I won't. I'll refer you to read the Machinery's Handbook. You'll need a little knowledge of trig and general math to completely understand threads. I'll take pictures of my thread-checking tools tonight and post them in a thread on machining tools for people to see. The subject of threads is a huge expanse of knowledge now, and MechE PhD could (and some  ave) written their PhD dissertation on esoteric issues in threading. When I say "Class 3" threads, I'm referring to how much engagement the thread has. A class 3 thread is the tightest fitting thread there is in the Unified thread system. Most bolts/nuts are Class 2 fits, and some really coarse bolts will be Class 1, designed to be screwed in with dirt, muck, etc on the threads and still fit. Class 3 threads demand that the threads be clean, clean, clean in order to get screwed together without messing up the threads or jamming the fit so tightly that you won't get them apart again.


Note: the MH has two editions: the "compact" edition that has remained the same size for over 100 years now, and the large print edition. Since I suffer from presbyopia just as most people do as we age, I now have the large print edition in addition to my small edition. If you wear bifocal safety glasses, you can read the small edition. I don't have any Gerstner toolboxes that have the handbook drawer in them, so most all of my MH's from here on out will be the large print edition.

For those who are wondering "What the ??? are you talking about Dave?" here, allow me to explain:

The top-end machinist's toolboxes are/were made by a company called Gerstner, made of American Oak, with felt-lined drawers, and these toolboxes have been the ultimate machinist's toolbox for over 100 years. The machinist version of their toolboxes has a drawer specifically designed for the Machinery's Handbook:

http://gerstnerusa.com/made-in-usa-products/chests-and-bases/2610-chest

See that odd-shaped drawer smack in the center of the toolchest? That's for the MH. Has been for 100+ years. The company that published the MH changes the information in the MH - taking some older stuff out, and putting newer stuff in, to keep the toolbox edition of the MH the same size it has been in order to fit into that drawer. The print size on the toolbox-sized edition is very small, but the quality of the printing is superb, and the pages are as thin as most Bible pages are. MH's have now become collectable of their own accord, with early editions fetching hundreds of dollars.

See the mirror in the lid of the box? Most folks are probably thinking "Those machinists must be a pretty vain group of guys." No, that's not why the mirror is there. In the days before safety glasses, when a man got a chip in his eye, he's use that mirror and a magnet to get the chip out of his eye. I suggest you use the mirror for vanity's sake and wear safety glasses instead. Gerstner toolboxes and bases are very, very nice. They make a great gift for someone who is a machinist, and they're very, very well built. The company has been owned/operated by the same family for four+ generations now, making high-quality toolboxes for craftsmen, machinists, woodworkers, etc.