Richard A. Huber, P. E
BC Hydro
Burnaby, British Columbia, Canada
Technical Services Committee Member
Introduction
The existence of counterfeit or substandard fasteners came to prominence in the United States in 1987 when the death of a construction worker was attributed to a bolt that broke unexpectedly.
The bolt was found to be made from substandard material. As a result, the Fastener Quality Act was introduced in the U.S. in 1990. The intent of this act was to establish regulations that would make it unlawful for a manufacturer or distributor to misrepresent the characteristics of a fastener. For each production lot of fasteners manufactured to conform to specific performance standards, samples must be tested by an accredited laboratory and the results documented in a record of conformance. This record must be made available by the manufacturer to distributors or individuals purchasing fasteners for use in commercial products. This requirement extends to imported fasteners.
Problem still exists
Unfortunately counterfeit or substandard fasteners still exist. In this article the reader will find information about fastener characteristics and suggestions to avoid purchasing substandard or counterfeit fasteners. The types of fasteners that will be discussed are those identified as standard hexagonal head SAE bolt grades 5 to 8 and hexagonal head metric bolt classes 8.8 to 12.9. The following information can, however, be used to avoid similar problems with other grades or classes of fasteners.
Counterfeit bolts have had the greatest impact on organizations that buy bolts in large quantities. Organizations in the United States such as NASA, Peterbuilt Trucks, Lawrence Livermore National Laboratories, Hanford Nuclear Facility and many others have been affected.
If organizations as large as the above can- not avoid purchasing counterfeit bolts, how can smaller companies with fewer resources tackle the problem? As daunting a task as this may seem, there are things that smaller companies can do to protect themselves.
The first precaution is to always buy from reputable suppliers. This applies worldwide. Even though the price might be slightly higher, these suppliers will be there toaccept your complaint and try to help you resolve an unsatisfactory situation. A less scrupulous company is unlikely to provide any assistance should its products be found unacceptable.
The second precaution, which particularly applies to companies in Canada or the United States, is to request from the distributor or supplier a copy of the test results applicable to the particular lot of bolts purchased. If the record of conformance is unavailable, then one might reconsider purchasing the bolts. One should also be aware that there have been instances where these documents have been forged.
Third, the bolts can be tested. A simple hardness check before using the bolts can identify those bolts that are grossly sub-standard. Alternatively, before using the bolts, subject them to a torque test in the service center to confirm that they will at least withstand the expected torque value. For bolts that are used in critical applications, it may be prudent to have the bolts tested by a laboratory.
The fourth item that small companies or individuals can do is educate themselves regarding the bolt standards and manufacturing procedures in their country and the characteristics of the various classes of bolts.
The following section outlines some of the more common bolt characteristics and standards. Armed with this information the purchaser may be better able to identify suspicious bolts.
Bolt characteristics
Bolts are typically characterized by the material from which they are made, physical dimensions and thread type. These characteristics are defined in one or more national or international standards.
Standards that apply to bolts
In the United States and other countries throughout the world, the standards that apply to bolts are many and varied. In the U.S., steel bolts used for most common applications are characterized by a combination of ANSI Standards, ASTM Standards, ASME Standards and SAE Standards (see “References” on Page 15 for the descriptions of these acronyms). Those that generally apply are shown in Table I.
Other countries may have their own standards for this purpose but many have adopted the applicable ISO Standards of which there are many. Those that apply to the most commonly used bolts are also shown in Table I.
Note unique markings
To help the purchaser/user identify bolts, many have unique markings. The symbols shown in Figure 1 are the more common ones. There are several others for bolts used in spe- cific applications. The ISO or metric bolt material identification marks usually appear on top of the bolt head but can also appear on the side of the bolt head on one of the flats.
In addition to the markings that identify the bolt material characteristics, the bolts must be marked with a manufacturer’s identification mark. These marks are registered in the U.S. with the
U.S. Patent and Trademark Office, Fastener Insignia Register. The manufacturer’s insignia usually appears on the top of the bolt head.
All the markings usually appear as raised letters or numbers on the bolt head.
Chemical composition
As shown above in Table I, there are several standards that describe the material characteristics of bolts. Note that the information in the following tables is for general comparison purposes only. For detailed information the reader should refer to the specific standard.
From the above tables one can see that the chemical specification for the materials for the various bolts is very similar. The addition of Mn and or B increases the hardenability of the material and may make it easier and more economical to process the manufactured products.
Mechanical properties
The standards listed in Table I also describe the mechanical characteristics of bolts. Once again it should be noted that the information in the following tables is for general comparison purposes only. For detailed information, the reader should refer to the specific standard.
From the preceding tables one can determine that the mechanical properties specified in the various standards are also very similar. The biggest difference is between the grade 5 material specified in the J429 standard and the 8.8 material in the other standards. This is important because the grade 5 material could be substituted for class 8.8 material. For practical purposes, the differences may not be significant but users should be aware of the differences to avoid any misapplications.
Conclusions
The distribution of substandard or counterfeit bolts is an ongoing problem which, as stated at the beginning of this article, can have very serious consequences. By performing four simple preventative measures, namely, diligently select suppliers, request test results when bolts are purchased, test bolts before use and become familiar with the standards that apply to metric bolts or inch series bolts, exposure to the serious consequences can be reduced. These actions, if followed by individuals worldwide, will help one avoid the problems that can result from the use of substandard fasteners.
References
- 101st Congress of the United States of America, “Fastener Quality Act, Public Law 101-592, November 16, 1990.”
- American Society of Mechanical Engineers, “ASME B1.1 Unified Inch Screw Threads.”
- American Society for Testing and Materials, “ASTM Standard F568M, Standard Specification for Carbon and Alloy Steel Externally Threaded Metric Fasteners.”
- Davis, J. R., “Metals Handbook, Second Edition,” American Society for Metals International, 2000.
- Euler, Garret D., “Standard Metric Bolt Properties, Grades, and Strength,” Structural Analysis Reference Library, 2002.
- Grogan, David and Demaret, Kent, “An Expert Warns that Cheap Bolts and Screws Can’t Hold the Country Together,” publisher unknown.
- International Organization for Standards, “ISO 68-1973, General Purpose Screw Threads- Basic Profile.”
- International Organization for Standards, “ISO Standard 898-1, Mechanical Properties of Fasteners made of Carbon Steel and Alloy Steel
- - Part I.”
- International Organization for Standards, “ISO Standard 965-1, General Purpose Metric Screw Threads - Tolerances Part I.”
- Nailen, Richard L., “Getting Down to Nuts and Bolts,” Electrical Apparatus, October, 1989.
- Nailen, Richard L., “Look Out for Substandard Fasteners,” Electrical Apparatus, February, 1992.
- National Institute of Standards and Technology, “Procedures for Implementation of the Fastener Quality Act,” Federal Register, Vol. 65, No. 125, June 28, 2000, Rules and Regulations.
- Society of Automotive Engineers, “SAE Standard J105, Hex Bolts.”
- Society of Automotive Engineers, “SAE Standard J429-1977, Mechanical and Material Requirements for Externally Threaded Fasteners.”
- Society of Automotive Engineers, “SAE Standard J475, Screw Threads.”
- Society of Automotive Engineers, “SAE Standard J1199-1983, Mechanical and Material Requirements for Metric Externally Threaded Steel Fasteners.”
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