[photo via Xyver]

[photo via Xyver]

Evaluating an industrial designer's skill level is a nebulous process. That's partially because our educations vary widely; while many of us had to protect an egg with cardboard at some point, there's no uniform test we all have to take and pass.

Machinists, on the other hand, have a little exercise that was purportedly once used to evaluate an apprentice's competence. It was something like a belt test in Karate, except you'd use a lathe and a mill rather than wearing a blindfold and fighting off flailing green belts.

"Twenty bucks says the blue belt is toast."

"Twenty bucks says the blue belt is toast."

The apprentice would be shown the object pictured up top (appropriately called a Turner's Cube), was given no instructions, and asked to crank one out on their own. The apprentice either figured it out and advanced to the next level, or presumably returned home to live with his mother.

[photo via Sean Ragan]

[photo via Sean Ragan]

These days you can easily produce one with a CNC mill, but that defeats the purpose; back in the day, you needed to have mastered a host of machine shop skills to produce the Cube. According to Instructables member Xyver, these skills included:

- Working within a +/- 0.005 tolerance (any more and it looks off)
- Dialing in a milling machine (to as tight a tolerance as you can get it, 0.001-0.002 is the goal)
- Using a face mill + planar bar on a mill to make the cube
- Facing cuts on a lathe
- Boring flat bottomed holes on a lathe
- Undercutting on a lathe
- Know how to dial in work pieces on a 4 jaw chuck

I'd like to think the apprentices were actually locked inside the machine shop and told they would not be allowed back out until the Cube was complete, but I can't find any evidence of this.