one- - over
- opacity
- open (sand) casting
- open annealing
- open area
- open boil of bath
- open butt weld
- open cast mining
- open core print
- open core print seat
- open die forging
- open dies
- open end
- open floor mold
- open forging
- open gamma field
- open groove
- open heart furnace
- open hollow section
- open joint method
- open light