The wonders of modern technology.
In a couple of hours. All the parts are accurate to within a few ten thousandths of an inch.
The switch from the 2024 aluminum test material to the 4340 steel part material required slowing the cutting speed by approximately 50% and increasing the feed rate by 25%. It may seem counter intuitive to increase the feed rate for a stronger material but the carbide insert's cutting edge needs to be able to get a decent bite into the material, otherwise it just deflects the workpiece and rubs, causing a lot of heat buildup and usually insert/tool failure which leads to a scrapped part.
Now that all 3 initial pieces are machined I will change the setup in the lathe to flip the part around and accurately hold it by the features we just machined. That post will be up soon.