The bolts always work together with a nut. A nut fastener is a mechanical fastener with a threaded hole. It is attached to a bolt, screw or stud to provide a clamping force and prevent axial movement. For example, a bolt is inserted through two parts, with aligned holes, and a nut is then screwed onto the bolt. The shaft of the bolt prevents radial movement of the parts, while the head of the bolt and the nut together prevent axial movement.
http://www.yuchaobolt.com/nut-fastener/

The bolts always work together with a nut. A nut fastener is a mechanical fastener with a threaded hole. It is attached to a bolt, screw or stud to provide a clamping force and prevent axial movement. For example, a bolt is inserted through two parts, with aligned holes, and a nut is then screwed onto the bolt. The shaft of the bolt prevents radial movement of the parts, while the head of the bolt and the nut together prevent axial movement.
http://www.yuchaobolt.com/nut-fastener/

Another indispensible equipment is steel pipe printing marking machine. Companies that produce metal pipes, regardless of whether they are involved in construction, aerospace, electronics, etc., code these materials to enable traceability, display important production data, and prevent counterfeiting. These codes generally take the form of numeric lot numbers or machine-scannable bar codes.

http://www.westwu-machine.com/....automatic-marking-ma

Another indispensible equipment is steel pipe printing marking machine. Companies that produce metal pipes, regardless of whether they are involved in construction, aerospace, electronics, etc., code these materials to enable traceability, display important production data, and prevent counterfeiting. These codes generally take the form of numeric lot numbers or machine-scannable bar codes.

http://www.westwu-machine.com/....automatic-marking-ma

The way a ball valve functions makes it easy to see if the valve is open or shut. The handle that operators use to adjust where the sphere is aligned with the flow when the valve is open, and it is perpendicular when the valve is closed. And the ball valve can be devided into many different types for different functions, such as floating ball valve, trunnion mounted ball valve, top entry ball valve, dbb ball valve, subsea ball valve, etc.

http://www.tfcvalve.com/ball-v....alve/floating-ball-v