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Fast Facts on Fasteners

Posted by Kimball Midwest on May 9, 2024

Tags: Fasteners, Grade 8, Fastener, Grade 5, Metric

Identifying a fastener can be difficult for some. The head markings can be difficult to make out, and they often are what gets disorganized in a shop first because of their small size.


This is where Kimball Midwest comes in handy. Our sales representatives are not only an asset at keeping fasteners in stock but also organizing them, teaching you tips and providing you safety measures.


Unfortunately, our sales reps aren’t always around for you to ask quick questions or get second opinions on all things fasteners. This is why we’ve created some fast fastener-related facts for you to keep in mind.


Identifying Marks


The head marking on a cap screw will help you identify the tensile strength and type/quality of steel used. Kimball Midwest cap screws are accurately manufactured to meet all requirements set by the Industrial Fasteners Institute.


The corresponding nut will be identified with similar radial markings, spaced by degrees or numbers identifying the class or grade. See pictures below.

Cap identification
nut fast facts-1




For fractional fasteners, threads are expressed in TPI or threads per inch.


For metric fasteners, threads are expressed in pitch (1.0, 1.5, 1.75), which is the distance between adjacent threads in millimeters.


You should also always verify your thread length for accurate fastener identification.


cap screw dimensions


What is Torque?


Torque is the force we exert at the end of the wrench times the length of the wrench. Best shown in the equation torque=force x length. Torque can be expressed in units of inch-pounds or foot-pounds and is measured by a torque wrench.


Most cap screw failures can be traced to insufficient strength for the application or improper tightening torque. Bending, stripping, breaking, twisting and stretching can all be caused by over-torquing. Always use a torque wrench on fasteners to avoid issues and failures.




Turn-of-the-nut is often referred to as mechanic’s feel. This is the approximate maximum amount of turn needed to produce the maximum safe clamp load possible without stretching the bolt to yield. Keep this in mind in terms of the length of the bolt.


Never Reuse a Nut


When a nut is torqued to the proper load, the cap screw elongates. This stretching, which occurs in the threaded area, naturally causes the pitch, or distance between the threads, to increase. The deformation of the threads absorbs additional torque, and less clamp force will be developed with the same torque in subsequent uses of the nut. Under this same torquing, the nut begins to compress. This decreases the nut’s thread pitch.


The pressure on the threads is concentrated at the lower end of the nut thread during initial loading. This pressure causes the threads to deform. So, the first two or three threads support 90% of the load, while the remaining threads support only 10% of the load.


Depending on the task at hand, Kimball Midwest can supply you with all your fastener needs in any specification.


Specifically, our Shop Setups are a great place to start. They offer organization, can be customized and come with popular options (Stainless, Metric 8.8 and Grade 8), all depending on what fasteners you need.


If you're ready to explore our fastener options further or need more facts, reach out to your sales rep today. If you do not already have one, we can help you Find a Rep!

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