HSS vs Cobalt Lathe Tool Bit

[Frank]

I have read the discussion on HSS vs Carbide lathe bits. It occurred to me that there is a 3rd alternative, Cobalt.
Is there any advantage/disadvantage to Cobalt vs HSS, since the cost difference is only about 50 cents for a 1/4" square, 6" long, 10% tool bit? I mean, specifically for cutting stem material.

[Benton]

I have read the discussion on HSS vs Carbide lathe bits. It occurred to me that there is a 3rd alternative, Cobalt.
Is there any advantage/disadvantage to Cobalt vs HSS, since the cost difference is only about 50 cents for a 1/4" square, 6" long, 10% tool bit? I mean, specifically for cutting stem material.

If you are having trouble with cutting vulcanite or acrylic on the lathe switching to cobalt tooling probably won't help. For soft materials, like plastic, the most important thing is to get your tools very sharp and HSS is the easiest to sharpen. With the right grinding wheel and a diamond hone you can can sharpen carbide tools too, but the benefits of carbide only really show up when you are cutting steel with them.
In our shop we use cobalt only for drilling stainless steel and for parting tools. We use HSS and carbide for machining steel or alumnium. For plastic we use HSS honed with a fine stone until it will shave off a thin sliver of thumbnail. If the tool slides over your thumbnail without digging in it is too dull for cutting plastic smoothly.