About the Author: This article was originally published in the March/April 2012 issue of the American Fastener Journal. The author, Guy Avellon, has been working in the repair industry for 30 years. He has served as manager of engineering management, marketing products and quality systems. Before joining the fastener industry, he was also involved in the metal coating industry. Since 1988, he has been a member of the SAE, serving as the vice chairman of the ASTM Fasteners Committee and concurrently chairman of the Fastener Test Method Committee. In 2005, Gay was awarded the Merit Award by ASTM. A few years ago, he opened a GT technical consulting company to train and analyze the failure of fasteners in various industries, as well as conduct ISO system audits and preparation of operating instructions. For about 35 years, I have been asked a lot about different fasteners: the use of fasteners, the screwing step, the cause of failure, how to prevent fastener failure, and so on. I have attended more than 1,000 fastener safety seminars organized by maintenance and industry organizations and private companies to demonstrate the problems in bolting and visually show how neglected variables affect clamping forces. This solves many problems. In this article, I have sorted through the many questions I have been asked over the years, including the use, selection, and expectations of fasteners, and answered these questions (or unanswered questions) in a concise language. Through this preface, I want to explain that in today's modern quality control system, fastener failure is often caused by hundreds of installation variables, improperly purchased fasteners, or improper assembly - and not Both are caused by product quality problems. Fastener selection 1. If the installation is not correct, the fastener can be invalidated. 2. The strength of the nut must always match the fasteners of its class. 3. Make sure that the fasteners and nuts used in the side-by-side connection are of the same grade. 4. A SAE (narrow) hardened flat washer must be used under the nut and bolt head. 5. In steel connections, USS (wide) hardened flat washers add more load area than SAE (narrow) hardened flat washers. 6. The fine teeth of the fastener (UNF) produce up to 10% more clamping force than the coarse teeth. 7. Rolling the thread on shear resistance produces 30% more shear resistance than cutting the thread. 8. Never cut on the rolling fastener to increase the thread. 9. Never confuse nuts and bolts with different surface treatments in side-by-side bolted connections. Fastener installation 10. In the connection, the difference in the length of the bolt thread will have different effects. 11. The bolt threads should always have at least one full thread extending out of the nut. 12. If the lock washer is not originally fitted to the fastener, do not put it on. 13. The lock washer does not prevent the preload from disappearing. 14. No locking device can permanently prevent the loss of preload. 15. Each connection is unique. 16. Impact wrenches must never be used to install fasteners. 17. The tightening is more important than the torque. 18. The wrenching technique affects the connection more than torque. 19. In the initial tightening of the fastener, the torque must never be fully applied, especially at a single connection point of multiple fasteners. 20. If this is a critical joint, the fastener should be retightened after tightening for two minutes and tightened again after applying the load. For more details on this article, please visit http:// to download the electronic version of the 29th Golden Spider "Fasteners" quarterly. Translator: Wang Weiwu Jin Spider Fastener Network Consultant Expert Transparent Case Steel Tape Measure 1. Shell: ABS new plastic, with shiny texture; anti-drop, wear-resistant, and not easy to deform. Transparent Case Steel Tape Measure,Rust Proof Tape Measure,Stainless Tape Measure,Metal Case Tape Measure Yucheng tengxu Measuring Tool Co., Ltd , https://www.txhardwaretools.com
a. There are hundreds of variables that can cause the clamping force to fail.
a. Improper selection of products may occur during the procurement phase.
b. It may also be mis-selected due to excessive inventory products during maintenance.
a. Sometimes fasteners are confused and placed in the same storage box.
a. The gasket is rarely marked, so F436 or hardened washers must be used explicitly.
b. Use hardened washers of grade 5 or grade 8.8 and above.
a. There is only one type of product that will increase the load area, that is, the flange face bolt nut.
a. This is because the area of ​​the force is different; (there are more thread stress faces in the same twist length due to the short pitch), and UNF has more metal material support.
a. This is because the cold work hardens and squeezes the crystal streamline.
a. Doing so will increase the stress point at the bottom of the thread and the tail of the screw (and cause breakage).
a. That is, the uncoated and laminated or different types of coatings are mixed.
a. The thread is the shock absorber and the stress point. Therefore, the thread length is increased in the dynamic load, and the thread length is reduced in the shear load.
a. This is to ensure complete threaded screwing in the nut.
a. Read it again.
a. The clamping force is significantly higher than the external service load, otherwise nothing can prevent the relaxation and pre-tightening force from disappearing.
b. See question 12.
a. If the joining material, fastener components and mounting torque are not appropriate, there is no guarantee that the preload will not disappear.
a. One of the connection methods you are currently using may not be suitable for another connection.
a. They are too difficult to control at the initial impact torque.
a. Relaxation occurs when one side is loose and the other side is tight.
a. How much can the connection point be compressed? Can the incremental torque mode be used?
a. Because the first tightened fastener will relax when the remaining fasteners are tightened.
a. This is the normal compression setting for materials, joints, and fasteners.
b. There are no shims that are not compressed. Every material will relax.
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8. Labeling: can be produced according to customer requirements.