Security Nuts That Shear Under Torque
Break away shear nuts are security nuts that break or shear under a certain pressure. These nuts are designed to be installed and never removed. You will often see them on street signs or in other places where vandalism may occur. These nuts are designed to have a structural flaw in them to create a breaking point.
The first step in installing these nuts is to hand tighten them onto a bolt. Once you get them snug against the installation material you will need to start tightening them with a wrench. Hold the bolt in place with a wrench and then grip the nut end from the other side with another wrench. Spin the wrench onto the nut side and as the nut tightens against the material (use a washer if the material is soft to avoid damage) it will begin to place force on the flaw.
Once the flawed area of the nut reaches its breaking point, half of the nut, the side with the hexagonal gripping area will break off, leaving only a coned end behind.
The end result is a secure fastener assembly that will be incredibly difficult to remove. The cone shape makes gripping devices such as vice-grips effectively useless at removal. The hexagonal end is considered a throw-away part and cannot be reused. Shear nuts are similar to tri-groove nuts in shape, however they do not have the grooves built in that are needed for removal.
Please Remember that these nuts are very difficult to remove. Make sure you only use them where you never intend on removing them again.