Torque is the force applied to something to make it spin (rotate) in machinery. Torque in relation to fasteners is the resistance faced when installing a fastener. Torque control then is simply controlling the amount of torque placed on a fastener without damaging it by over-tightening.
Measure of a screw or nuts frictional resistance to rotation.
Prevailing “Off” Torque
Highest back-off torque on a torque wrench on the first rotation of a screw or nut upon removal.
The initial torque amount used to install a fastener before Pre-load.
The minimum torque required to start rotation into a nut (in the case of a bolt) or into a pre-tapped hole (in case of a screw).
Minimal torque required to begin the disassembly of a fastener assembly.
The torque required to produce pressure onto the installation material causing compression by the fastener.
Torque Wrenches are one of the easiest ways to ensure proper torque is met. Simply set the wrench’s torque and then when the maximum is reached the clutch will slip. This slip means the wrench stops putting any more torque on the fastener and it has reached its optimal 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.
The first thing we need to do when installing a carriage bolt is to make sure we have the right parts and tools to do so. For this job we will need a:
Piece of wood
For our example, we have already pre-drilled the hole into a piece of 2×4 and attached it to a vice. This will act as our installation surface for our carriage bolt.
Understanding A Carriage Bolt
A carriage bolt is a bolt with threading all the way up the shank to a small square shoulder, with a domed head. The square shoulder of a carriage bolt stops it from spinning as it is screwed into the surface of a material. You would not typically use this type of bolt on very hard wood as it may not properly dig into the material, which would cause the bolt to spin in place. Once you seat the bolt through the hole, it is the job of the nut and washer to pull the bolt into the material tightly. Since there is no drive device for the domed head of the bolt, this is the only way to install it.
The installation process is fairly simple. First you drill a hole into the wood for the appropriate size (diameter) of the bolt. Next you slide the bolt into the hole (you may need a hammer as the hole should be just big enough for the bolt to go through).
Now that you have the nut through the wood it is time to attach the nut and washer. Place the washer on the rear side of the bolt followed by the nut. The washer will help to distribute the force you are about to put onto the nut to pull the bolt into the wood. This will not only protect the wood on the back side but also keep the bolt from digging into it and getting stuck.
As you tighten the nut, the square shoulder on the bolt will be pulled into the wood. Once the underside of the head rests against the wood, the carriage bolt is officially installed.
Removing the carriage bolt is a fairly simple process. First, you will want to twist the nut loose to the end of the bolt. DO NOT TAKE THE NUT ALL THE WAY OFF THE BOLT, you will need it to help move the bolt along.
Once the nut is backed off to the end of the bolt, hit the nut with a hammer. The force should start moving the square shoulder out of the wood. As you move the bolt further out the nut will get closer to the wood. When this happens continue to back out the nut and strike it again. Repeat this process until the bolt is loose enough to take out by hand or the nut can no longer grip the bolt.
If you find the bolt is stuck but the nut can no longer attach to the bolt, use the nail remover attached to the hammer and use it to pry the bolt out of the hole.
It’s That Simple
There you go now you know everything you’ll need to know about installing and removing carriage bolts. As always, Albany County Fasteners stresses the need for protective gear while working with dangerous materials. Remember to ALWAYS wear safety glasses while drilling to protect your eyes and wear protective gloves that fit to keep your hands safe from harm as well.
Keps K lock nuts are nuts that have a free spinning serrated washer attached to them. These nuts are made to create tension against the material when installed onto a bolt. It is important to NEVER over torque these nuts. Once you over tighten a lock nut it loses its functionality.
The picture below is a hand tightened keps k nut with no added torque. You can see the teeth are pressing lightly against the metal material we have installed the bolt through.
Once we have tightened the bolt very lightly you can see the teeth have extended out to create tension against the object. If you over-tighten this type of lock nut you will ultimately flatten out the teeth and when you remove the nut you will see that the teeth no longer perform any function they will just act like a washer.
Keps K locks are ideal for applications where you might use an external tooth lock washer and nut but the combination is more convenient. You need to carry around fewer parts making installation much faster. They also save you from the fumbling of little lock washers that seem to be designed to fall from your hands and disappear.
Tri Groove security nuts are nuts that are installed with a very unconventional drive. These nuts have three slots in them, making them unique in shape and appearance. They have a cone shape, designed to be gripped only by the device intended to tighten and loosen them.
You can commonly find these in places where security or vandalism is a concern. To test these nuts we decided to install one ourselves and test a couple of different tools to see if we could remove them quickly.
First, we installed the nut using a tri-groove socket tool specially designed for this drive style. After install, we attempted to tamper with this fastener ourselves to determine what it would take to remove it.
We tried using an adjustable wrench. That didn’t work, the cone shape of the nut showed no gripping areas to lock the wrench into. We also tried pliers which had the same effect. Vice grips were our last attempt to break this nut loose with a conventional tool. However, the cone shape made it incredibly difficult to find a locking point. So we attempted to grab the lip and the base of the installation. The lip proved to be too small to get a good grip, leading us to our conclusion.
Having tested several different removal methods for removing this nut, we have determined that without either the proper tool or physically altering the shape of the nut (perhaps with a grinder) to provide a gripping point for more conventional tools, it is unlikely that this nut will be easily tampered with when installed correctly.
*Although these nuts are fairly secure there is still a chance that someone could have enough know-how or time to alter the shape of the nut or may have come across the proper tool to remove them.