I made an attempt to start my home-built Saiga-12 muzzle brake last night. I didn't get very far.
About 5 years ago, right when I first bought my mini-mill, I purchased a bunch of bar stock and round stock from a salvage metal yard. The steel had surface rust on it when I bought it.
I chucked up one of the round ingots for the brake. The ingots are about 5" long, and measure 1.25" OD. I didn't realize that even after 5 years, the surface rust had not progressed.
Using my trusty carbide cutters, I began facing the ingot to true it up. That's as far as I got. After the rust layer was removed, the nice shiny steel laughed at the carbie cutter that was trying to cut into it. All I managed to do was create a thin hair-like shaving that got orange-hot because the cutter wasn't doing anything but scraping, making heat.
Sparks were flying! The 316 stainless steel I use to make pistons is like butter compared to this stuff!
The metal looks more silvery than the "grey-white" I normally see on the softer 1018? that I usually cut on.
The cuts are concentric and some of the ingots appear to have a centering dimple on the ends.
I'm guessing something like the 4340 that I have? It looks closer to 4340 than any other steel I have in the shop. What could this be from? I have a whole bunch of ingots that I am not going to be able to use for anything but paper weights, considering how tough they are. Perhaps an automotive axle that was cut up...? Is it even suitable for machining? It could make some mighty fine rifle bolts...
I'm afraid if it is 4300 steel (or worse) then I'm probably out of luck, because my tools simply can't handle this stuff. And that's too bad, because I have a bunch of it. I also have some HUGE rounds, one that is 8" diameter x about 8" tall. And quite a few 4" rounds.
Any thoughts on how to make this easier to digest on the lathe? Different cutters perhaps?