Review on Hole Back Plate - HHIP 3900 3215 by Michael Vargas

It has the threads specified but does not thread easily into my South Bend lathe with those threads. The reason is that behind the threads, the lathe has a short unthreaded section, and the diameter there is slightly larger than the thread, and there is no corresponding gap in this article. I corrected it with a short drill. Because of the way it's made, it's actually cast iron and not steel. I don't have any equipment to measure the carbon percentage, so I can't say for sure.