page_title: Set screw
section_title: Point types
hierarchical_section_title: Set screw / Point types
caption_attribution_description: English: Allen Manufacturing Company Inc advertisement for the Allen Safety Set Screw, a brand of set screw, in the Automobile Trade Directory, January 1913.
context_page_description: A set screw, also known as a blind screw or a grub screw, is a type of screw generally used to secure an object within or against another object, usually without using a nut. The most common examples are securing a pulley or gear to a shaft. Set screws are usually headless, meaning that the screw is fully threaded and has no head projecting past the thread's major diameter. If a set screw does have a head, the thread will extend all the way to the head. A set screw is almost always driven with an internal-wrenching drive, such as a hex socket, star, square socket, or a slot. The set screw passes through a threaded hole in the outer object and is tightened against the inner object to prevent it from moving relative to the outer object. It exerts compressional or clamping force through the bottom tip that projects through the hole.
  An example application is when a set screw is screwed into a pulley hub so that its end-point bears firmly against the shaft. The fastening action is by friction between the screw and the shaft, often with some amount of elastic or plastic deformation of one or both.
context_section_description: Set screws appear with a variety of tip (point) types. The different shaped tips have different properties that engineers can utilize. If an engineer were to use a detent to ensure proper nesting of the screw, they might choose to use a cone point type of screw. One might often need to use a flat point when the screw must press perfectly flat against a surface. The most common type is the cup point. This type works well because the surface is rounded so that a small surface area is in contact, but it does not have extremely high stress at one point like that of a cone point. Durability studies show that the cup point offers superior resistance to wear while maintaining a strong grip. Knurled cup points offer the added advantage of a locking action (similar to that of a serrated lock washer) that prevents the screws from working loose in high-vibration applications.
  Common points include the following:
  Flat point
  Domed point
  Cone point
  Cup point
  Extended point (pilot point, dog point)
  Knurled cup point
caption: This advertisement from 1913 illustrates various set screw point types
exif: {}