How to Measure the Length of Different Fasteners

I find that there is often some confusion on the proper way to measure flat head, shoulder and hex or socket head screws. I realize this may be a simple, almost trivial discussion for many, but perhaps worthy of a review. At C.I.S. we continually strive to communicate effectively in order to understand our customers' needs. Insuring that we receive the correct measurements from you, our customers allows us to supply the product you indeed want. If confusion surrounds the measurement of fasteners, it can certainly lead to shipping delays and then the worst of all, production delays.

The following are simple diagrams that will show you how to measure the length and diameter of the fastener.

  

 s

 

To measure the length of a shoulder bolt you must only measure from under the head to the end of the shoulder body. Please do not confuse this with the other fasteners and measure the overall length and include the threads.

Please include the diameter of the shoulder when ordering. When measuring a shoulder bolt please be aware that you do not measure the threads or the diameter of them. The threads will be a standard size that corresponds with the shoulder diameter. Example: If the diameter of the shoulder is 5/16 the threads will be 1/4-20. If the diameter of the shoulder is 3/8 the threads would be 5/16-18.

 Top of page

Hex Cap Screw Strengths

As salespeople we are often asked questions pertaining to the strengths of hex cap screws. In this article I will provide you with a quick reference chart. The chart shows the materials used in manufacturing along with proof, tensile and yield strengths of hex cap screws.

The cap screws most commonly ordered have strengths referred to as grades 2, 5 and 8. The grade 2 is the weakest manufactured with a low carbon steel. The grade 8 is the strongest of the three manufactured with a medium carbon alloy steel, quenched and tempered. If you have an assembly requiring a large amount of preload or strength, a grade 12 manufactured from alloy steel, quenched and tempered is available. There are two classes of metric fasteners included in this chart. Often there is confusion regarding the strength of metric bolts. Please note that a class 8.8 is not a grade 8. The class 8.8 has properties stronger than a grade 5 bolt but less then a grade 8. The class 10.9 cap screw has properties similar to the grade 8 but less strength to the grade 12.

To follow is a chart with technical information relating to the mechanical properties and the grade markings of hex cap screws. I refer to this sheet often and find that our customers appreciate having it as a quick reference.

 Top of page