For basic lathe training in my shop classes(bygone 30years past) we made C-clamps, center punches and ball peen hammers.
Although the C-clamp was a mill/lathe project, it did include many basic skills required for machine operations. Lathe turning the screw threads, knurling the screw head and cross drilling for a slider bar, Drilling and tapping the frame after the profile was cut. Turning a swivel foot and swedging it onto the screw end. A bit more than a few hours I suppose, but if broken into sub-projects it makes a nice little clamp on course completion. I still have all mine.
The center punch also had knurling and taper turning. Drilling and reaming the business end for a press fit insert point that required heat treating 0-1 drill rod. You could come up with similar projects like scribes with carbide tips made from tungsten welding electrodes.
Small vise jaw stops are another mill project.