Thick, hexagonal head with a washer face under the head provides an ample bearing surface for tightening with a wrench. This secure yet removable general purpose threaded fastener is designed for insertion in pretapped holes or for use with nuts. Hex-head cap screw is a small but critical part that helps keep your production running smoothly. Finding the right screw for your project is essential. Minimum thread length is calculated using the screw’s length. The formula is dia. X 2 + 1/4”.