| 29 / | HD | METAL WORKING |
| 592 | DF | METHOD OF MECHANICAL MANUFACTURE {54} |
| 890.03 | DF | .~ Heat exchanger or boiler making {15} |
| 890.045 | DF | .~.~ Tube with heat transfer means {1} |
| 890.046 | | .~.~.~ Finned tube {4} |
| 890.047 | DF | .~.~.~.~> Common fin traverses plurality of tubes |
| 890.048 | DF | .~.~.~.~> Helically finned |
| 890.049 | DF | .~.~.~.~> Internally finned |
| 890.05 | DF | .~.~.~.~> Made from unitary workpiece, i.e., no assembly |