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Last Post 20 Mar 2001 08:42 PM by  Lemke
SAE Grade 5 vs Metric 8.8
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ScottNutter
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20 Mar 2001 11:47 AM
    I am prepping an 83 RX7 for ITA and of course some of the bolts along with the roll cage bolts will end up being new. I would like to use metric bolts because in some instances it's the right thing to do and in others for convienience of knowing that I only need my metric tools at the track. The GCR states sizes and grades in english/SAE standards, dimensions are easy but is the metric specification of 8.8 the equivilant to grade 5 or do I need to get 10.9 bolts?

    Thanks
    Davard
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    20 Mar 2001 07:32 PM
    Since M10.9 is roughly equivalent to grade 8, I believe that 8.8 is similar to grade 5.

    Tensile strength of a grade 5 is 120,000psi, where grade 8 is 150,000psi at an elevated temp, although I don't remember what that temp is. Grade 8 bolts are more brittle than grade 5.

    Maybe you can find some specs for metric fasteners that would compare to this data.

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    David Avard
    '90 Mazda Protege LX
    Lemke
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    20 Mar 2001 08:42 PM
    FYI...

    8.8 = approx. 116,000 psi (800N/mm2)
    9.8 = approx. 130,000 psi (9000N/mm2)
    10.9 = approx. 145,000 psi (1000N/mm2)
    12.9 = approx. 174,000 psi (1200N/mm2)



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