I gotta ask... is that drill head decorated? Or is there a purpose for all those welded-on lines and dots?.
Them lines are what what is known in the welding trade as hard-facing. It's put on there to postpone wear to the actual surface of the cutting head. Excavator buckets and bulldozer blades typically have the same thing. It's done by running a bead of weld from a special hard-facing welding rod all over the surface to build it up.
Although the drill is pretty big, not as large as a roadyway tunnel.
Another little light just blinked on. Just this past week we started twin tunnel boring in East Los Angeles. We have 2 TBM's (tunnel boring machines), each about 21' diameter. I'll see if I can get some pictures together during the week.
There are 10 types of people. Those who know binary, and those who don't.