I purchased this block of round stock off eBay. Was told it is 1045. Realizing I need to slice in half and couldn’t fit in my band saw I figured I’d mill four flats. Wow, have to tell you that was something else it was extremely difficult to machine. I machine 1045 gear stock all the time and never experienced anything like this. I noticed the excessive shaking and pounding right away. I proceeded, swapped cutters out for carbide, it helped, and then decided it was a bit rough on my tooling and mill I called in the white flag and pulled out the Rockwell test kit. 65hrc? Nope it scratched, 60hrc? Nope it lightly scratched, 55HRC? Yep the file slid across the surface. Uhmm that’s not 1045 unless someone hardened it but we’re not talking surface hardening. There isn’t any carburizing that’s been done to this. It’s very raw looking yet and I tested where I cut a good 1/4” off the rounded side. This has a 55HRC internal hardness. I think I may have a different material on hand. Any educated guesses? Unless it was through hardened but the seller made no mention nor does it look like it’s gone through the process. I harden 1045 steel at least once a week so I’m familiar with the process and you typically have those tell tale signs. Only thing remotely suggesting hardening is the scaling on the outside but it looks more like a rust treatment to me.