Bolt Grade Help

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Jun 19, 2013 | 06:59 PM

Foxknuckle

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Cruiser

Joined: Feb 2013

Posts: 158

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From: Oregon

Bolt Grade Help

I need to replace the lower shock bolt on my FXDB with a longer one to accommodate a license plate bracket. The bolt appears to be a grade 8 bolt and the only thing I can find locally is a 12.9 hardened alloy bolt. Will this bolt work?

Jun 19, 2013 | 07:03 PM

SLV

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Joined: Oct 2012

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From: Outside the Lines

Grade 8 is a hardened alloy, but I don't recognize the 12.9 designation. It must be a Euro thing.

Let me look in my engineering cross reference book. Stand by please.

Jun 19, 2013 | 07:31 PM

SLV

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From: Outside the Lines

The 12.9 is a rating system of metric sized alloy steel fasteners. The 12.9 fasteners out perform grade 8 fasteners in yield and tensile strength. (12.9 = 160ksi yield and 177ksi tensile, the grade 8 = 130ksi yield and 150ksi tensile.)

The "alloy" steel 12.9 material is more corrosion resistant than grade 8 carbon steel too. (Carbon steel is also an alloy, so the term can be confusing.)

The Klinger rating is used for metric fasteners though. The lower shock bolt on our 2013 Street Bobs is a 1/2" x 13 American Standard.

If you have access to the correct size in a Klinger 12.9 rated alloy steel fastener, you are in good shape. It's a better fastener than a grade 8.

Jun 19, 2013 | 08:20 PM

Foxknuckle

Thread Starter

Cruiser

Joined: Feb 2013

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From: Oregon

Thanks a lot! I feel better knowing.
By the way SLV love your bike, it was one of the inspirations when buying mine.

Jun 19, 2013 | 08:22 PM

SLV

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Joined: Oct 2012

Posts: 4,423

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From: Outside the Lines

Quote:

Originally Posted by Foxknuckle

Thanks a lot! I feel better knowing.
By the way SLV love your bike, it was one of the inspirations when buying mine.

Glad I could help, on both accounts! Thanks for the kind words.

Jun 19, 2013 | 08:25 PM

maddghost

Ultimate HDF Member

Joined: Apr 2008

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From: Out on Deranged

Wow SLV that is some good info right there!

Jun 19, 2013 | 08:35 PM

SLV

Elite HDF Member

Joined: Oct 2012

Posts: 4,423

Likes: 47

From: Outside the Lines

Quote:

Originally Posted by maddghost

Wow SLV that is some good info right there!

Thanks. I learned it at the same time. In 25 years of engineering, I've never used Klinger rated fasteners. These would be great for hot rod builds. Especially 4 links and 9" rear ends.

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Jun 20, 2013 | 12:30 AM

Pistonman1

Road Captain

Joined: May 2012

Posts: 608

Likes: 42

From: Kingston, Washington

I was putting a turbo on a Cat scraper today, new Cat bolts were rated 12.9, and they were SAE size (3/8-16).

Jun 20, 2013 | 05:48 AM

#10

FastHarley

Former Sponsor

Joined: Apr 2007

Posts: 5,360

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From: Davie, FL

I use them

I use those bolts for my caliper mounts I make to hold on radial mount calipers. I want to make sure they do not stretch or break. They will rust so a coating is necessary.