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The notches allow efficient sorting of a large number of cards in a paper-based database, as well as the selection of specific cards matching multiple desired criteria. Unlike machine-readable punched cards , edge-notched cards were designed to be manually sorted by human operators.
Some punch designs use hollow punch heads (a thin-walled tube), with the edge a sharpened blade. This allows the chads to be pushed up and out the top, as the paper is being cut, making it more suitable for thicker volumes of paper. For very large amounts of paper, a paper drill may be used instead of a punch.
The punch force required to punch a piece of sheet metal can be estimated from the following equation: [4] F = 0.7 t L ( U T S ) {\displaystyle F=0.7tL(UTS)} Where t is the sheet metal thickness, L is the total length sheared (perimeter of the shape), and UTS is the ultimate tensile strength of the material.
The heart of the 024 and 026 keypunches was a set of twelve precision punches, one per card row, each with an actuator of relatively high power. Punch cards were stepped across the punch one column at a time, and the appropriate punches were activated to create the holes, resulting in a distinctive "chunk, chunk" sound as columns were punched.
A paper tape, constructed from punched cards, in use in a Jacquard loom. The large holes on each edge are sprocket holes, used to pull the paper tape through the loom. Perforated paper tapes were first used by Basile Bouchon in 1725 to control looms. However, the paper tapes were expensive to create, fragile, and difficult to repair.
An IBM 80-column punched card of the type most widely used in the 20th century IBM 1442 card reader/punch for 80 column cards. A computer punched card reader or just computer card reader is a computer input device used to read computer programs in either source or executable form and data from punched cards.
Numeric columns have one punch in rows 0-9, possibly a sign overpunch in rows 11-12, and can be sorted in a single pass through the sorter. Alphabetic columns have a zone punch in rows 12, 11, or 0 and a digit punch in one of the rows 1-9, and can be sorted by passing some or all of the cards through the sorter twice on that column.
Die roll takes the form of a radius around the outside edge of the blank and the pierced holes. After compression, the part shears for about 10% of the part thickness, and then fractures free of the strip or sheet. This fracturing produces a raised, jagged edge which is called a "burr". Burrs are typically removed by tumbling in a secondary ...
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