Flats, Keys, and Taper Pins

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Flats, Keys, and Taper Pins

• By Steve Merdzinski

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Flats

• A flat is a surface which is produced by milling
  a portion of an external cylindrical surface.
• Flats are generally made to prevent the turning
  or slipping of pulleys, collars, and other things
  that could be connected to shafts.

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How to Dimension a Flat

• To Dimension a flat you must dimension the length
  between the flat itself and the surface it will
  be locked against.
• You must also dimension the space between the
  bottom of the hole and the bottom of the notch
  that the flat is pressed against.

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Keys Taper Pins

• Fasteners which are used to join and prevent
  rotation of two or more assembled machine parts.
• Generally, one part is the shaft, and the other
  is what the shaft fits into, such as a pulley,
  gear, wheel, cam, propeller, or crank.

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Keyseats and Keyways

• The Keyseat is a groove which is cut in the
  mating part, so that the key fits partly into the
  shaft and partly into the mating part.
• The Keyway is the slot in which the key fits
  into.

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Types of Keys

• Woodruff key
• The Flat key
• The Gib-head key

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Woodruff Key

• A Woodruff key or half-moon key, is a
  semicircular shaped, removable key that fits into
  a matching keyway cut into a shaft, leaving a
  protruding tab. The tab mates with a matching
  slot on a device.

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The Flat Key

• A long rectangular device with parallel sides and
  precise dimensions that is inserted into a
  matching keyway and key slot.
• Sometimes also called a bar key

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The Gib-Head Key

• A device similar to a standard bar key, except
  with a head at one end that extends above the top
  surface of the key.

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Taper Pins

• Similar to keys but are often removable
• A semi-permanent, cylindrical pin that has a
  slight taper along its length. Taper pins are
  often used on parts that require frequent
  assembly and disassembly.