Grade 8 bolt question
Thread Starter
Melting Slicks
Joined: Jan 2001
Posts: 2,940
Likes: 5
From: Chesapeake VA
Grade 8 bolt question
I need to replace a metric bolt that broke on my daily beater. I want to use a Grade 8 bolt, but it is metric and I think it uses a different rating system (8.8, 9.8, etc). What grade should I ask for when purchasing this bolt?
Thanks! :seeya
P.S. - Sorry for it not being quite on topic, but I looked in Off topic and they were talking about Ron Jeremy, so I thought you guys would be a better place to start.
Thanks! :seeya
P.S. - Sorry for it not being quite on topic, but I looked in Off topic and they were talking about Ron Jeremy, so I thought you guys would be a better place to start.
Racer
Joined: Feb 2001
Posts: 298
Likes: 1
From: San Antonio Texas
Re: Grade 8 bolt question (Square)
You need to replace it with the same strength bolt. A grade 8 SAE bolt does not have the same strength as a metric 9.8, for example.
The metric may be slightly more expensive, but when you are dealing with "high strength" fasteners you don't want to skimp; the results can be disastrous (remember about 10 years ago when small, private planes had their propellers falling off frequently? The problem there was using a "foreign" grade 8 bolt instead of a USA bolt; the "foreign" stuff was cheaper, but did not have the same strength requirement to meet as the US standard :eek: ).
Best bet is to get an exact replacement for your broken bolt; metric 8.8, 9.8, or whatever it is.
The metric may be slightly more expensive, but when you are dealing with "high strength" fasteners you don't want to skimp; the results can be disastrous (remember about 10 years ago when small, private planes had their propellers falling off frequently? The problem there was using a "foreign" grade 8 bolt instead of a USA bolt; the "foreign" stuff was cheaper, but did not have the same strength requirement to meet as the US standard :eek: ).
Best bet is to get an exact replacement for your broken bolt; metric 8.8, 9.8, or whatever it is.
Le Mans Master
Joined: Feb 2000
Posts: 5,708
Likes: 1
From: Bedford NH
Cruise-In II Veteran
Re: Grade 8 bolt question (John Nowak PE)
Actually there is a relationship, but it is not an obvious one. Mr. Nowak is coerrect, you should not mix them. There is a BIG difference between a SAE grade 8 and a ISO(metric) grade 8.8!
On my web site I published an Excel spreadsheet that does give a conversion based on material properties:
http://www.hardbar.net/Fastener%20Grades.xls
On my web site I published an Excel spreadsheet that does give a conversion based on material properties:
http://www.hardbar.net/Fastener%20Grades.xls
Thread Starter
Melting Slicks
Joined: Jan 2001
Posts: 2,940
Likes: 5
From: Chesapeake VA
Re: Grade 8 bolt question (ghoffman)
Thanks for the replies guys!.
I should add that I am not looking to use a "Grade 8" bolt, just something that is strong like a "Grade 8" bolt. When the bolt broke off, the head fell off completely, and I was left with the end in the nut (which fortunately I was able to unscrew by hand!). Without the head, I do not know what the original metric grade of the bolt was, so I thought I would just get the strongest bolt I could find in that size. The car is an 85' Thunderbird and the bolt is from the Powersteering pump mounting bracket (the pivot point, not the adjustment arc bolt). I will try to look up the torque spec for that bolt and go from there. I assume it dosen't hurt to put in a stronger bolt than is required as long as you don't over torque it? :seeya
[Modified by Square, 2:07 PM 1/7/2002]
[Modified by Square, 2:07 PM 1/7/2002]
I should add that I am not looking to use a "Grade 8" bolt, just something that is strong like a "Grade 8" bolt. When the bolt broke off, the head fell off completely, and I was left with the end in the nut (which fortunately I was able to unscrew by hand!). Without the head, I do not know what the original metric grade of the bolt was, so I thought I would just get the strongest bolt I could find in that size. The car is an 85' Thunderbird and the bolt is from the Powersteering pump mounting bracket (the pivot point, not the adjustment arc bolt). I will try to look up the torque spec for that bolt and go from there. I assume it dosen't hurt to put in a stronger bolt than is required as long as you don't over torque it? :seeya
[Modified by Square, 2:07 PM 1/7/2002]
[Modified by Square, 2:07 PM 1/7/2002]
Le Mans Master
Joined: Aug 2000
Posts: 5,529
Likes: 1,943
From: Austin Texas
Re: Grade 8 bolt question (Square)
In a situation like this, I always go for aircraft blots/nuts/washers. Some Grade 8 bolts are brittle, aircraft parts never are. Many times I can find these parts for less maney than their automotive equivalents.
Racer
Joined: Feb 2001
Posts: 298
Likes: 1
From: San Antonio Texas
Re: Grade 8 bolt question (Square)
Yes Square, you are correct; a stronger than necessary bolt won't hurt anything.
If you are having a hard time figuring out what bolt you had, a good Ford service department/parts department should be able to tell you (for free) what bolt goes in there. I would suspect, however, that a grade 8 would likely work just fine for you.
I hope this helps :cheers:
If you are having a hard time figuring out what bolt you had, a good Ford service department/parts department should be able to tell you (for free) what bolt goes in there. I would suspect, however, that a grade 8 would likely work just fine for you.
I hope this helps :cheers:
Pro
Joined: Aug 2001
Posts: 608
Likes: 0
From: Las Vegas NV
Re: Grade 8 bolt question (John Nowak PE)
FYI.....Just to inform everyone a Grade 5 is close to a 8.8 and a grade 8 is close to a 10.9. There is no such thing as 9.8. In the ride amusement field we interchage many metric to SAE. Just remeber Grade 5 = 8.8metric and Grade 8 = 10.9metric. Just thought I would put my .02's :chevy
Safety Car
Joined: Dec 2000
Posts: 4,786
Likes: 0
From: God Bless America
Re: Grade 8 bolt question (John Nowak PE)
If you are having a hard time figuring out what bolt you had, a good Ford service department/parts department should be able to tell you (for free) what bolt goes in there. I would suspect, however, that a grade 8 would likely work just fine for you.
I hope this helps :cheers:
I hope this helps :cheers:
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