Thread type description of the hottest self tappin

Description of thread type of self tapping screw

identification characters of standard self tapping screw, including symbols representing thread and tail shape Self tapping screws have one or two characters representing thread to represent mechanical thread or wide thread (spaded) For example, the identification character "B" represents a wide thread screw Those without "B" represent mechanical threads The tail representative character is used to distinguish the self tapping screw from thread forming, cutting, rolling or self drilling

the mechanical thread has the same thread angle of 60 degrees and the same pitch of coarse and fine threads as the British and American unified thread. If the screw is lost after disassembly or if necessary, it can be replaced by standard thread fasteners

the wide thread has a thread angle of 60 degrees, but its pitch is generally wider, and because of its wide pitch, its thread is steeper, so its thread guide 1. The installation process is larger than the mechanical thread There is another kind of thread specially used for plastic, with a thread angle of 48 degrees, commonly known as Pt thread screw

thread forming self tapping screws a, AB, B, BP, C and other types have been gradually replaced by thread rolling self tapping screws, so it is not recommended to use them in the new design AB, B and BP differ only in the shape of the tail. AB has a threaded cone tail, B has a blunt tail, BP has a non threaded cone tail, and the center of the sharp tail enters the pre drilling and starts to form the thread Thread cutting self tapping screws have the forms of BF, BP, D, F, G and t. BF and BP are wide threads, and the rest are mechanical threads

the difference between recognition characters is their cutting tail Each cutting tail has a shape that can collect the waste material under cutting If the self tapping screw is screwed into the blind hole (non through hole), its fragments will remain and be sealed at the bottom of the hole However, if the through hole is drilled, the waste will fall on the other side of the workpiece Therefore, this must be considered when selecting this type of self tapping screw. Waste materials may cause pollution, fall into running parts or make the electronic substrate inoperable

all thread rolled self tapping screws are mechanical threads, which is the same as the coarse thread of metal material thread, which has become the second largest in industry use at present, after steel and iron. Please refer to SAE J81 regulations Refer to SAE j1237 and din7500 for metric threads

there are two types of self tapping screws with cutting wide thread BSD and mechanical thread CSD In addition, there are special thread types, including high and low double threads, and various tapping and drilling tails are also applicable Because the prices of base metals and precious metals are still difficult to improve in 2014, tail drilling screws are not suitable for blind hole operations When assembling self drilling screws, the drill tail needs to completely penetrate the workpiece before cutting or forming the thread, so there will usually be some debris. If thread cutting threads are used, there will be debris Therefore, this problem must be considered in practice For BSD and CSD drill tail screws, please refer to SAE J78 and DIN7504 (wide thread)