When you are using any types of fasteners, one of the most important things you can do is ensuring that the amount of torque used to put them in place is just enough. Usually, tightening the fasteners too much can result in exceeding of the tolerances of the fastener. For instance, you may end up stripping some of the threads on a screw, making it ineffective. If the forces acting on the metal exceed its plastic limit, it means that it may end up stretching and not recoiling back to its original size, which in turn means that it will not hold the structure together.
One of the ways of avoiding this problem is by testing the fastener torque either when you are putting them in place or when you just want to find out if they have been installed properly. Doing this accurately is usually very important when the tension in the fasteners has to be calibrated to within a particular range. Some of the methods of testing torque in fasteners such as titanium hex lag bolts include:
The first movement test
In this test, you will need to use a wrench that has a torque meter on it. Usually, these can be rented or bought cheaply online. Using this method to find out the torque in an installed fastener involves rotating the fastener in a clockwise direction, as you would when tightening it. The goal is to try to make it move just slightly so, and then note the torque reading when this first occurs. It’s important that you don’t move the fastener too much, particularly if it’s very tight and is within its limits.
The loosening test
This is similar to the first movement test. The only fundamental difference is that in the loosening test, you would be trying to undo the fastener, and then note the recording the first time this happens. This method of testing torque is most ideal when you are working with a fastener that has been tightened such that any further tightening might result in damage to the material you are fastening, or failure of the fastener. When you are using this method, it’s important to not be too enthusiastic, since you may end up loosening the fastener too much.
Using the marking test
This is a method that is more or less subjective, but it’s still applicable. To use it, you will need to mark the fastener as well as the area around it. You will then need to loosen the fastener, and then try to retighten it such that the marks that you had placed earlier end up being aligned again. One of the major benefits of using this test is the fact that it’s very easy to do. You can use it for most types of fasteners including Nylon screws.
In summary, it’s always very important to pay attention to the amount of torque used to place fasteners. The above are some of the common methods of testing the torque to make sure that they are in place firmly.
Started my career in the fastener world in 1969 at, Parker Kalon Corp. a NJ based screw manufacturer located in Clifton, NJ working in inventory control, scheduling secondary production and concluding there in purchasing. In 1971 I accepted a sales position at Star Stainless Screw Co., Totowa, NJ working in inside sales and later as an outside salesman, having a successful career at Star I had the desire with a friend to start our own fastener distribution company in 1980 named: Divspec, Kenilworth, NJ. This was a successful adventure but ended in 1985 with me starting Melfast in August 1985 and have stayed competitive and successful to date. Melfast serves the OEM market with approximately 400 accounts nationally.