Views:2 Author:Site Editor Publish Time: 2018-06-11 Origin:Site
Bolts and screws are both Building Fasteners that help to position objects and hold them together. Some say that bolts are screws but not all screws are bolts. There are not really hard set distinctions between bolts and screws but they do have a few specifications. Some examples of screws are Headcote Screws, Heavy Hex Screws and Hex Cap Screws, examples of bolts are Heavy Hex Bolts. So, what’s the difference between bolts and screws?
What are Screws?
An externally threaded fastener, designed for insertion through holes in assembled parts is called a bolt. It is usually intended to be used along a nut. If it has a head on one end it is a screw. The head is driven or turned with a screw driver or sometimes with a wrench. The diameter ranges vary to meet demands and needs of specific products. Screws are generally turned into an object, like a piece of wood, so the head needs to be bigger than the surface. This prevents the screw from being turned further than the length of the screw itself. There are a few exceptions. For example, set screws have smaller heads and have special uses. There are a few screws that are tightened counterclockwise but most of them are tightened by turning clockwise.
What are Bolts?
Bolts are screws that rotate into a matched nut to tighten it. Bolts have a bigger head than the shaft, with a few exceptions. Carriage bolts and J-bolts are among those exceptions. The shafts of bolts are not tapered, whereas many screws are tapered.The main difference between a bolt and a screw is that a typical screw can work on its own and a bolt requires a nut to secure it. An externally threaded fasteners capable of being inserted into the holes inside assembled parts (now comes the difference) of mating with a pre formed internal thread or forming it's own thread is called a screw. It has an ability of being tightened and released by torquing the head.
As we can see a screw has the space on it's head to suppy torque.
The Machinery’s Handbook describes the distinction as follows:
A bolt is an externally threaded fastener designed for insertion through holes in assembled parts, and is normally intended to be tightened or released by torqueing a nut. A screw is an externally threaded fastener capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread, and of being tightened or released by torqueing the head. An externally threaded fastener which is prevented from being turned during assembly and which can be tightened or released only by torqueing a nut is a bolt. (Example: round head bolts, track bolts, plow bolts.) An externally threaded fastener that has thread form which prohibits assembly with a nut having a straight thread of multiple pitch length is a screw. (Example: wood screws, tapping screws.)
After reading this, you should have a better understanding of the difference between screws and bolts.