In the 2000 Presidential election, much ado was made about the appearance of "dimpled chad" and "pregnant chad." Before getting into how these effects in punch carts are produced, we need to understand what they are. A few definitions:
In the 2000 Florida elections, several counties used the Documation card reader pictured above on the right. It reads standard IBM punch cards, and converts the pattern of holes punched in the cards into information. The cards are put into the card reader. The computer attached to the reader reads the cards, and counts the votes punched into them.
But it is the way these card readers read cards that is of interest in this election scenario. The picture on the right shows the basic mechanism. As the card feeds through the reader, a set of sensing pins is pressed against the card. The pins rapidly touch and move away from the card, once for each of the 80 columns of punch positions on the card. The sequence of operation is as follows:
That's the way it is supposed to work. But unfortunately, little bits of dust fall off the punch cards as they pass through the reader. Those bits of dust tend to accumulate on the pins. This has an effect on how the card is read. With card dust coating them, the pins need more force to be retracted into the ram. This puts more force on the card - a force that can dimple the chad.
To prevent the creation of dimpled chad, the instruction book for the Documation card reader gives a procedure for determining whether or not the reader pins need to be cleaned:
It was once the page author's job to administer these tests, change out a card reader that needed servicing, and to clean the pins. The next hurdle comes when you try to clean the card reader pins today. The instructions say to use a Freon spray (such as Blue Shower) to clean the pins. But the government has since banned Freon sprays, so a good substitute must be found to maintain these card readers.
Another twist is that these machines were not really designed to use the preperforated Votomatic cards. Those cards were designed to be used with optical card readers. But an optical card reader made in the 1970s cost several times what these Documation readers cost, so Florida counties bought the cheaper card readers.
In the case of the Florida elections, the Documation card readers had not been cleaned in several years. This meant that the dust-coated pins made nice dimpled chad when the card reader was used to read the votes. And when they did the recounts, the sticking pins dimpled the chad even more, making some of them into pregnant chad.
All that remained was for the Democrats to discover the dimpled and pregnant chad, and to try to turn them into uncounted votes. But there is no way a voter could make a rounded indentation with the square stylus provided for the voter to use. Only the rounded pins in the card reader can do that.
So, instead of the dimpled and pregnant chad being attempts to vote, they were the products of card readers that had not been serviced in years.