Metric Fastener Styles and Grades

Screws, bolts, and nuts that are classified based upon the metric system are referred to as metric fasteners. Fasteners can be used to secure materials that will be used in either an indoor or outdoor environment. The size of a product should be adequately assessed, before purchasing metric fasteners. In addition, the style and grade of the material should be considered.

The Style

Screw and bolt heads feature a countersunk or non-countersunk design. A countersunk design will lay flat when two materials are joined together. This type of product is often used in applications where the appearance of a product is important, such as in residential and business settings where aesthetics are considered.

A non-countersunk design will consist of a screw or bolt head that is fully exposed. With either head style, the imprint that runs across the top of a metric fastener will dictate what type of tool is needed to drive the metal component through two materials that are being adjoined together. A slotted head will require a flat blade screwdriver and a Phillip head will require a Phillips head screwdriver.

Some imprints will require a hex key or torx head screwdriver. When shopping for metric fasteners, acquire the proper measurement and inspect the head design and imprint, to ensure that you will have the proper tool to complete the installation of the hardware pieces.

The Grade and the Coating 

The metric grading system consists of a series of numbers that are separated by a dot. The number is indicative of the tensile strength of a metric fastener. A higher value will indicate that the steel is more durable than a steel fastener that contains a lower rating.

Metric fasteners may contain a non-corrosive coating. This material will increase longevity and is often used in applications where weather resistance is essential. An example of an application that would require the use of metric fasteners that contain non-corrosive coatings is the installation of marine docking materials.

With this type of application, the installer of a dock will not need to replace fasteners frequently or worry about the materials being compromised, due to a rust covering that detracts from the appearance of the other docking materials. After purchasing a supply of fasteners, keep them organized, by placing them in a bin that contains separate drawers that can be labeled. Use the labeling system to outline how the metric fasteners will be used.