[John Welden]

Is there a type of stainless that is:

Machinable
Has decent spring characteristics
Doesn't need heat treat after machining

I need to make a stainless collet

Thanks,
John

[andypugh]

"Spring" is more about design than material. Traditional spring materials are defined by having a high ratio of yield strength to tensile limit, but that just makes them more efficient as springs.
To further complicate matters, "machinable" is a rather woolly concept, and the existence of CBN (Cubic Boron Nitride) and diamond tipped tooling has stretched that boundary in much the same way as Carbide did, and High Speed Steel before that.

Have a look around www.matweb.com Perhaps 440C would do what you need.