Tool Steel - What do I have?

[Bob Korves]

Keep your eye for Rex bits also. Some of the Rex bits rival carbide for wear resistance, but are tolerant of interrupted cuts. I use Rex bits in my fly cutters and pull light blue chips with no issue to the cutter. They are the right tool for cutting the grunge off of cast iron and hot rolled.

Rex did make a bunch of different classes of bits, so they are not all the same. Which ones are you referring to? I do agree that Rex tool bits were/are very high quality, regardless of their typically rough finish. Edit: Rough finish of the bits, not the work...

 

[joshua43214]

I have some Rex 49 bits that I abuse the daylights out of. My understanding is that it is considered one of the ultra-hard high speed steels (whatever that means). I just know I can put buckets of tool pressure on it and it not only stays sharp, but the edge breaks down nicely as it fails. Oddly, it grinds easier than the M8 HSS blanks I often use for my steel cutting. The ones I have a smallish, so they are best suited for flycutting or short stick out on the lathe.