Ordinary people can't distinguish screws, even if many mechanical engineers can distinguish them, it is really unreasonable, screws seem simple, but there are few people who understand them.
Two days ago, I wrote an article about Japan's 14.9 grade ultra-high-strength screws, see → for details, and many people in the comment area said that screws were bolts, and I was speechless at that time, and I couldn't even distinguish between screws and bolts, and I dared to comment in the comment area of my article.
1. Definitions
Bolt is called bolt in English, and bolt translated into Chinese means bolt, latch, bolt, latch, deadbolt.
Screws are called screw in English, and screw translated into Chinese means spiral, screw, propeller. Obviously, the screws are all fully threaded.
螺柱,的英文是stud,指没有头部,仅有两端均带外螺纹的一类紧固件。 如双头螺柱(double end stud)、焊接螺柱(welding stud)等。 全螺纹的螺柱被叫作螺杆。
The screw is rotated into the threaded hole; The bolt is inserted into the through hole and is locked by a nut at one end; The studs are headless smooth rods and are locked by nuts at both ends.
2. Classification
Classification of bolts: semi-round head bolts, countersunk head bolts, square head bolts, high-strength bolts, hexagonal head bolts, studs.
Classification of screws: concave screws, non-ejection screws, positioning and shaft screws, machine screws, set screws, wood screws, special screws, self-tapping screws, self-tapping locking screws, self-drilling and self-tapping screws.
3. Bolts
Bolts are widely used in detachable connections in machinery manufacturing, generally used with nuts (usually plus one washer or two washers), the bolts are directly inserted into the hole, the bolts do not rotate, and the nuts are locked.
4. Screws
The screw is usually used alone (with washer and elastic pad as needed), generally playing a fastening or tightening role, and should be screwed into the internal thread of the body and rotated and tightened.
5. Studs
Stud STUD is mostly used to connect one of the connected parts with a large thickness, and it is necessary to use a compact structure or a place where bolting is not suitable due to frequent disassembly. Studs are generally threaded at both ends (single-ended studs are single-ended threaded), usually one end of the thread is firmly screwed into the body of the component, and the other end is matched with the nut to play the role of connection and fastening. Since the stud does not rotate during the tightening process, the stud only experiences tensile stresses, therefore, in general, the stud performs better than the bolt.
6. How to use
When the bolt is used, it is directly inserted into the through hole of the two connecting plates, and the nut is used to lock, and the screw needs to make a threaded hole on the substrate, and the screw rotates and screws into the threaded hole, as shown in the figure below, the bolt on the left, and the screw on the right.
Finally, screws, bolts and studs must be selected with a focus on performance levels. The highest performance class is 12.9 for steel screws and A4-70 for stainless steel screws. GB/T 5783 Hexagon Head Bolt Full Thread Performance Grade up to 10.9 (steel), GB/T 5780 Hexagon Head Bolt C Performance Grade Only 4.6 and 4.8.