Varieties of Screws/Bolts

Wood Screw

• • Has a sharp point.
  • Generally has an unthreaded shank below the head.
  • Designed to attach 2 pieces of wood.

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Sheet Metal Screw

• • Use sharp points and threads and are designed to be driven directly into sheet metal. They can also be used in softer material like plastic, fiberglass, and wood.

  • Self Drilling Sheet Metal Screw

    • Sheet metal screw with a self-drilling point.

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Machine Screw

• • Smaller fastener threaded the entire length of the shank.
  • Usually has a recessed drive type.
  • Has
a
• • a thread class
. 
• • Thread-Cutting Machine Screw

    • Machine screw with a thread-cutting (self-tapping) point.

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Set/Grub Screw

• • Is headless.

  • Fix a rotating part to a shaft.

  • Used only for transmitting very light loads.

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Socket Screw

• • A machine screw with an internal hex socket (Allen) drive. longer lengths may have a smooth upper shank.

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Shoulder Screw/Bolt

• • Shank is ground to a precise diameter and threaded portion is smaller in diameter then the shoulder. These fasteners can be used to create a pivot point.

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Barrel Nut/Mating Screw

• • Used for through-bolting applications where a head is desired on both sides of the joint.

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Fastener Heads

Flat Head

• • A countersunk head with a flat top.

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Round Head

• • A domed head.

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Oval Head

• • A countersunk head with a rounded top.

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Hex Head

• • A hexagonal head, can have a washer or flange modification.

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Slotted-Hex-Washer Head

• • A hex head with a built-in washer and slotted drive.

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Button Head

• • A low profile rounded head using a socket drive.

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Socket Head

• • A small cylindrical head using a socket drive.

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Drive Types

Socket/Hex/Allen Drive

• • Hexagonal hole for use with an Allen wrench.
  • Often used in bicycle maintenance and furniture.

Phillips and Frearson Drive

• • An X shaped drive.
  • Designed to cam-out after a certain torque limit.

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Slotted Drive

• • A slot in the head, used with a flathead installation tool.
  • Most popular.
  • Less likely to have rounded or stripped slots.

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Combination Drive

• • A combination of slotted and Phillips drives.

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Square/Robertson Drive

• • A square-shaped drive type.
  • Often used in automotive and furniture industries.
  • Has the highest torque tolerance.

Star/Torx Drive

• • A six-pointed star pattern specifically designed to prevent cam-out and stripped heads.

One-way Drive

• • Installs with a normal slotted or "flathead" installation tool but can not be removed without special tools.
  • Often used on barrel nuts and mating screws.

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Varieties of Screw/Bolt Heads

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