Shoulder screws are a type of machine screw with integral threads that are only present on half or less of the screw shank. A shoulder screw has a partially smooth shaft that will allow the bolted material some rotation and movement around the screw axis, while the threaded end will typically have a nut to maintain the screw's position. These screws must be used with predrilled holes, and are common in machinery with vibration and heat variations.
Socket shoulder screws known as shoulder bolts, stripper bolts or precision shoulder screws have a plain (un-threaded) shoulder section located between the head and the thread.
The plain shouldered section is larger in diameter than the threaded section of the fastener and is commonly used as a pivot, shaft or stationary guide in applications such as pulleys, cams, gears, latches etc.
The outside head of the socket shoulder screw is commonly ‘knurled’ allowing better manual tightening and grip from the user / installer.
