When looking at the head of a bolt, there are six details that can be told by them: the type of fastener (or drive type), the grade (or classification) of the fastener, the manufacturer, the material type, the plating or coating and whether it is an Imperial fastener or a Metric fastener.

These details can be broken down into various groups called Grades or Classes that classify them according to their property ranks, quality, degree and other various facets. According to Imperial (SAE) and Metric specifications, as the grade and class of the fasteners increase, so do that of the bolt’s tensile strength.

How a Recoil Wire Thread Insert Works: Recoil wire thread inserts are rolled from high quality stainless steel wire with a diamond shaped cross section, wound to the shape of a spring thread. Once the insert is installed into a tapped hole, it provides a permanent and wear resistant thread in the parent material that is stronger than the original thread.

Recoil inserts are greater in diameter than the corresponding tapped hole and compress as they are installed. This allows maximum surface contact area with the tapped thread, safely and permanently anchoring the inserts into place.

The kind of hole to be tapped has much to do with the style of tap that’s best suited. Some holes go all the way through. Others, while not through holes, still are relatively deep. Some are quite shallow, little deeper than diameter. Each of these three kinds of holes through, deep-bottoming blind, and shallow bottoming, has a tap or group of taps best suited to requirements.