Screw Classification By Purpose
Screws can be divided into three categories: machine screws, set screws and special screws.
Main machine screw set screw hole for a part with a fastening with through-hole parts, do not need to meet a nut (this form of connection is known as a screw connection, also belong to the removable connections can also tie in with the nut, two fastening with through-hole parts. ) Is the most common type of screw.
Set screws are mainly used for fixing the relative positions between the two parts. Slang we call "screw", acts as locating pins.
Special screw for lifting rings, screws and other parts, for example.
Grades of carbon steel bolts 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, over more than 10 levels, before and after the decimal point of the number represent the nominal tensile strength and yield ratio of bolting material, such as: Mark grade 8.8 bolts material tensile strength of 800MPa and yield ratio was 0.8 per cent yield strength 800X0.8=640MPa