Screws, bolts, screws, what is the difference between the three ah?
Screws and bolts have a clear professional terminology, there is a clear distinction, should not be arbitrarily named. Screw and bolt classification has more than 100 national standards, only the standard of the screw there are 92, the standard too much, not convenient memory, not listed one by one, but there are rules to follow, you can simply distinguish: all round And fasteners made of threaded rods are called screws. It must be screwed with a screwdriver, a slotted countersunk head screw, a countersunk head screw, a hexagon socket head screw, a hexagon socket head screw, etc. Set screws, all kinds of set screws, do not take off screws, axial screws; all kinds of knurled screws (with knurled without tools to tighten); there are wood screws and tapping screws and so on. Fasteners with hex head, square head and threaded rod are called bolts.
Screws are more general. The exact statement should be bolts, screws, and screw caps. Bolts and screws are round bar objects, engraved with equal spacing thread. Bolts are flat head cylindrical type; the screw is the front is pointed like a nail. The bolts must be used with the screw cap, or on objects that have been threaded. Screws are used in relatively soft or relatively thin objects, when used with their own thread side of the rotation side of the forward drilling. The threads on the bolts are relatively shallow without the edges; the threads on the screws are sharper and the threads are deeper, facilitating drilling into the objects. Most bolts and screws require a simple and easy tool - the screwdriver.
The screw is an incorrect call, non-professionals on the threaded parts collectively, in the industry without this call. In the fastener industry, in fact, screws and bolts are not a strict sense of the distinction. However, there are two ways in the industry to distinguish between screws and bolts: 1. According to the structure, the so-called twist structure, refers to the screw / bolt used to put the wrench above the place, that is, In some systems inside, the external pull the structure of the external screw rod-shaped parts are all called the bolt, on the contrary, will pull the structure called screw. This is a more obvious example is the Chinese national standard fasteners, for example, GB5782, GB5783 (a half thread, a full thread), the hexagonal bolts, The Because they are hexagonal structure, so, in the standard name, all called: bolts. 2, according to whether the product has a non-threaded bar features to distinguish. This is also a relatively wide use of a classification method, are generally so distinguish between bolts and screws. That is, if the part of the product other than the head is threaded, this part is called a screw. On the contrary, if, in addition to the thread but also has a light rod and other characteristics, called the bolt
There are no hexagonal head but the middle of the screw with the middle of the pole known as the double-headed bolts (studs), the whole body is screw called screw, in addition to countersunk head neck bolts, T-slot bolts, anchor bolts, U-shaped bolts. Bolt tightening device for the torque wrench, the opening size of the various shapes of fixed wrench, the opening variable size of the movable wrench, hydraulic tight bolts need hydraulic pumps and other accessories. In short: fasteners with screwdrivers and hexagonal tools are screws, and fasteners with wrenches are bolts. Note: can not be distinguished by the size and length of the nominal diameter. For example, a M48 long 300mm cylindrical head fasteners, GB / 70.1-2008 standard will be defined as hexagonal head screws, not bolts.
