When you are looking at choosing a fastener you need consider your purpose for the fastener and what kind of threading will be best suited for the job. They type of threading that a fastener has can determine the strength and what kind of job the fastener will be best suited for. There are two types of threading that you can use: find threading or coarse threading.
Advantages of a Coarse Threaded Fastener
If you need the fastener that you are going to use to have good fatigue resistance you should choose a coarse threaded fastener because when thread pitch increases, stress concentration will decrease. Shipping and handling can cause a lot of wear and tear on fasteners and coarse threaded bolts tend to handle better in the shipping and handling process. They also tend to assemble easier because they are less likely to cross-thread. If the fasteners are to be used on brittle material you should use a coarse threaded fastener, as well. It is almost much more difficult to strip the threads on a coarse threaded bolt or screw. Finally, they also tend to be more resistant to corrosion.
Advantages of a Fine Threaded Fastener
If higher tensile strength is a priority to you, the fine-threaded bold is your best choice because it has a larger tensile stress area. They also have larger minor diameters, which results in higher degrees of both transverse and torsional strengths. Hard and thin walled materials require fasteners that can penetrate more easily and fine-threaded fasteners tend to be better for this. When you are working with materials that are likely to undergo vibrations, either because of machinery that is associated with it or the environment in which it is situation, you need a fastener that is unlikely to come loose, so you should choose a fine-threaded fastener.
Before you choose a fastener, you should understand what the purpose of the fastener will be. You should know what to expect from it and be familiar with the task that the fastener will assume. This will help you to choose a fastener that is best suited for the job.
Based on the advantages alone, I would go with fine threaded fasteners for aerospace hardware because there is too much vibrations involved in take off and landing. Very informative piece!
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