Thats odd about the email. I've always gotten very good service from them, thats why I recommend them all the time. I guess they do seem to like doing business over the phone rather than email though. Anytime I have to email them about something they always call back rather than email
It doesn't have to be O1 either. I recommend it because its easy to heat treat. If you've got a controlled oven, your already ahead of the game though and could use stuff thats more complex. Just need to get the specs on it, and learn a little bit about heat treating and what to look for. There are a couple different standards used for naming steels also, you might find similar stuff under a different name. ASTM and AISI/SAE use different systems for naming the same stuff.
ASTM uses letter designations, looking at function first, then strength, then chemistry. Unfortunately I can't find my list for them.
AISI uses a 4 number designation. The first 2 digits tell the alloy used, and the last 2 digits give the carbon content. For example, 1084 is a plain carbon steel with .84% carbon content.
5160 on the other hand has a little less than 1% chrome added and .60% carbon content.
6150 has chrome and vanadium, and a carbon content of .50%
AISI uses a different code for what are considered "tool steels" . These steels have a letter telling which category they fall into. A( medium alloy air hardening), O(oil hardening), D(high carbon high chrome), S(shock resisting) for example, then a number designating which one of the group they are.