I turn again to my trusty engineering friends after reading an earlier thread here, the difference between a screw and a bolt, checking out the Bolt Science Glossary, scanning through many pages of wikipedia and scouring countless manufacturer's web-sites. What the heck is a CAPscrew .............

Its me again, last time it was screws and bolts, now I'm working on the section of the tariff dealing with pipes and tubes, iron and steel. The tariff breaks down some pipes according to their American Petroleum Institute grade. Can anyone give me a website that explains what H-40, J-55 or K-55...