With the development of economy, the use of the bolt screw area were also expanded, now has been widely used in aerospace, instrument, electric, chemical fiber, hydraulic and other fields. Material: conventional has two kinds of stainless steel and carbon steel Standard: metric and standard divides into two kinds. Metric specifications for industrial grade 6 h precision, the standard of grade 5 h precision; American standard specification of industrial products for 2 b precision grade, the standard of grade 3 b precision. Correct installation process: drilling, tapping, screwing (installed) - to press the pin into