I was just curious what the op’s intent was. Maybe he has a link to his thread on it. Dave
Music wire becomes another source to look at if you are having difficulty getting materials. As long as it comes straight and not rolled up. I believe you may be overly focused on the hardness. As nervous mentioned, it’s good practice to harden and temper which gives a bit softer material but allows it to spring back to shape if it experiences slight bending. It’s a trade off. I really think the HSS is the way to go. One suggestion would be to keep the actual weight of poppet to an absolute minimum. Not only does the stem have to crack the seal it has to accelerate the mass of the poppet. The set screw weight may be working against you. Just a suggestion. Dave