Show and Tell

Q. ¿Qué son compuestos pará limpiar y pulir accesorios metalicos? (What are compounds for cleaning and polishing metal parts?)

A. Here I am in the Republic of Panama, enrolled in a Spanish class, and I forgot that my column is due. Great! I was telling my classmates what I do for a living, mass finishing and all that stuff, and found myself explaining an ordinary industrial process to people in a country that has virtually no metalworking industry. Not a single classmate nor maestro has ever set foot in a metalworking factory—not one. That surprises me in light of the fact the one of the greatest engineering feats of all time, The Panama Canal, is right here and about three miles from our
classroom.

Quickly, I pulled out some coins—Canadian and Panamanian—and tried to explain how these are made. Of course, most are stamped, but some are powdered metal. All I wanted to do was explain edge breaking and burnishing. You can’t imagine how quickly that got out of hand. It is not uncommon to hear media called “stones,” so I started into that concept; I tried to explain man-made stones. What? Well you know what canicas are, don’t you? They are made-made stones that we call marbles back in the States. Kids played with them before computers took over their minds and hands (and their parents’ money).
Of course tumbling media are not made of glass. They have to be less friable, and they usually require an added abrasive. So, they are made by extruding clay through an orifice of a particular geometric shape, such as a circle or a triangle. Then, equally spaced parallel wires cut this clay extrusion so that the cut pieces are all the same shape. Sort of like squeezing toothpaste out of a tube, I said. Holding up a pencil, and explaining how this could be cut into angle cut cylinders got me through that one. It was easy to then explain that these pieces must be fired in a kiln just like the pottery and ceramic items so common in this area.

Someone then asked if the shapes can be made more accurately by molding or casting them, similar to making aspirin pills – she had seen that done, and she opined that it seemed faster, and maybe cheaper, than cutting them from an extrusion. OK, so we talked about pill pressing, slip casting and other methods. That led to plastic media and detracted significantly from the “stone” analogy. It was soon obvious that we were off the track.

All this, and we had not touched on the machines used in this strange process. I thought I would skip over the tumbling part and get right to vibratory finishing, so that I would have time to introduce disc finishing. What a mistake! Try explaining vibratory finishing equipment when you omitted the basics of a tumbling barrel! I think tumbling barrels are probably easier to explain than vibrating bathtubs and doughnuts. I hope I get another chance to find out.

Show and tell time was over, and I never explained compuestas, but my classmates were already proud of their new knowledge and class ended on a happy note.