I'm interested in making watching lathe tools and ultimately replacement parts for watches. I would like to get started by buying steel material but am thoroughly confused about the types of steel available. Could somebody explain to me the characteristics of and differences between the following:
1. Ground steel plate
2. Mild steel
3. Drill rod
4. Tool steel
5. Flat steel stock
6. Steel cold rolled
7. Any others I should know about
I also would like to know where I could purchase small quantities of steel.

You may want to pick up a copy of the Machinist Handbook Rich.It will answer all your questions plus provide you with a wealth of info pertaining to machining and forming of the various tool steels.Most libraries usually carry a copy or two .
Best of luck in your endeavor.
Respectfully,Bob Fullerton

Mild steel is a low carbon steel. It is used for building brackets and other supports. Welding steel, hot rolled, cold rolled are various forms of mild steel. Most have a carbon content of about half a percent.

Tool steel is a high carbon steel with about 1% carbon. This is appropriate to use to build tools that cut or pound. It can also be used to make springs, winding wheels and staffs. It comes in several forms. One of the oldest is W-1. When you heat it up to cherry red and cool it quickly in water, it is very hard and brittle. When it is then polished and reheated to form various colors on the surface, it is partially softened to make it an appropriate hardness for various uses. We can discuss this more if you widh.

Another common tool steel is O-1. It has to be heated slightly hotter and cooled in oil to harden it. It is annealed in a similar fashion. There are dozens of other tool steels, but they are of little interest in vintage watches.

Most Drill rod is made of a tool steel. Some is high speed steel (HSS) that is not useful, because it takes a much higher heat to harden and temper. So most drill rod is 0-1 or W-1 in cylidrical shape.

You can purchase these steels and learn a little about them at MSC. See http://www1.mscdirect.com/cgi/nnsrhm

Here is a page from their catalog that describes some of the tool steels http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=1717&PARTPG...CTLG=00&PMT4TP=*LTIP

The next page is drill rod. It gives the composition of these steels.

http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=1718&PARTPG...CTLG=00&PMT4TP=*LTIP
I use W-1, because it is the oldest form of tool steel. The fellow I work with prefers O-1, because it resists forming microcracks when it is harded and cooled in oil. Otherwise they are very similar. You see that W-1 has to be heated to 1425 F to harden, while O-1 has to be heated to 1450 F. That is not much of a difference. You see that A-2 has to be heated to 1725 F, which is difficult for us to reach with small torches or alcohol lamps.

You can search the other names that interest you at the MSC site and see what kind of steel they use.

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