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This guide is an introduction--and a warning--about "inferior" Grade 8.2 bolts. Grade 8.2 bolts are attractive because of their low cost in comparison to "true" Grade 8 bolts. There is a reason they are less expensive.
What is Grade 8.2, and how is it different from "true" Grade 8 bolts?
SAE Grade 8 refers to the highest "standard strength" achieved in the manufacture of "American fine or coarse thread" (not metric) bolts and hex head cap screws. Grade 8 bolts are medium carbon alloy steel, quenched and tempered at a minimum temperature of 800 degrees Farenheit. They are then heat-treated to achive a hardness of 33 to 39 on the Rockwell C scale.
By comparison, Grade 8.2 are low carbon martensite steel, fully killed, fine grain, quenched and tempered at a minimum temperature of 650 degrees F. Grade 8.2 fasteners are heat treated to achive hardness of 35 to 42 on the Rockwell C scale.
Two issues with Grade 8.2 fasteners: 1) They fail from relaxation at elevated temperatures; and 2) industry experience shows that bolts with hardness values over 39 are prone to embrittlement if not properly processed during manufacture. In certain applications, using a Grade 8.2 bolt in a Grade 8 application could result in failure.
The layman's translation: Grade 8.2 can stretch (and break) when hot, and they may be more brittle (which can result in breakage) than a true Grade 8 bolt.
The United States Nuclear Regulatory Commission (NRC) has written extensively about bolt failures due to the use of Grade 8.2 bolts that were used where "true" Grade 8 bolts were specified. See the NRC Information Notice No. 89-59 "SUPPLIERS OF POTENTIALLY MISREPRESENTED FASTENERS" for confirmation. In the case of the NRC, the substandard Grade 8.2 bolts were misrepresented as "true" Grade 8, and so they are considered "counterfeit" bolts. Please remember that even if the seller is honest enough to tell you that they are Grade 8.2, they still suffer from all the problems--and potential failures--that the NRC experienced.
In addition, the National Highway Traffic Safety Administration (NHTSA) started an aggressive campaign to eliminate the use of counterfeit and substandard bolts by vehicle and component manufacturers. Peterbilt had to recall 556 tractors in 1988 because of Grade 8.2 bolts, and Freightliner of Canada recalled 364 tractors.
If you're seeing auctions for "Grade 8/8.2" bolts, you might want to ask the seller specifically which of the two grades are you going to receive.
You might want to check out my "other" stainless steel bolt guide
If you've found this guide helpful, please give me a "Yes" vote by clicking the button below. If you have suggestions for improvement, you can contact me through the "My Messages" feature of eBay. Click on my user name at the top of this page, then click on "Contact Member". Thanks, all!
Entire contents copyright (C) 2007, 2008 Camino3X2 Feel free to LINK to this Guide in your auctions.
What is Grade 8.2, and how is it different from "true" Grade 8 bolts?
SAE Grade 8 refers to the highest "standard strength" achieved in the manufacture of "American fine or coarse thread" (not metric) bolts and hex head cap screws. Grade 8 bolts are medium carbon alloy steel, quenched and tempered at a minimum temperature of 800 degrees Farenheit. They are then heat-treated to achive a hardness of 33 to 39 on the Rockwell C scale.
By comparison, Grade 8.2 are low carbon martensite steel, fully killed, fine grain, quenched and tempered at a minimum temperature of 650 degrees F. Grade 8.2 fasteners are heat treated to achive hardness of 35 to 42 on the Rockwell C scale.
Two issues with Grade 8.2 fasteners: 1) They fail from relaxation at elevated temperatures; and 2) industry experience shows that bolts with hardness values over 39 are prone to embrittlement if not properly processed during manufacture. In certain applications, using a Grade 8.2 bolt in a Grade 8 application could result in failure.
The layman's translation: Grade 8.2 can stretch (and break) when hot, and they may be more brittle (which can result in breakage) than a true Grade 8 bolt.
The United States Nuclear Regulatory Commission (NRC) has written extensively about bolt failures due to the use of Grade 8.2 bolts that were used where "true" Grade 8 bolts were specified. See the NRC Information Notice No. 89-59 "SUPPLIERS OF POTENTIALLY MISREPRESENTED FASTENERS" for confirmation. In the case of the NRC, the substandard Grade 8.2 bolts were misrepresented as "true" Grade 8, and so they are considered "counterfeit" bolts. Please remember that even if the seller is honest enough to tell you that they are Grade 8.2, they still suffer from all the problems--and potential failures--that the NRC experienced.
In addition, the National Highway Traffic Safety Administration (NHTSA) started an aggressive campaign to eliminate the use of counterfeit and substandard bolts by vehicle and component manufacturers. Peterbilt had to recall 556 tractors in 1988 because of Grade 8.2 bolts, and Freightliner of Canada recalled 364 tractors.
If you're seeing auctions for "Grade 8/8.2" bolts, you might want to ask the seller specifically which of the two grades are you going to receive.
You might want to check out my "other" stainless steel bolt guide
If you've found this guide helpful, please give me a "Yes" vote by clicking the button below. If you have suggestions for improvement, you can contact me through the "My Messages" feature of eBay. Click on my user name at the top of this page, then click on "Contact Member". Thanks, all!
Entire contents copyright (C) 2007, 2008 Camino3X2 Feel free to LINK to this Guide in your auctions.
Guide created: 07/08/06 (updated 09/04/08)
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