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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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New Member

New Member

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?


    Veteran Member

    Veteran Member

    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.

    David Avard
    '90 Mazda Protege LX

    New Member

    New Member

    20 Mar 2001 08:42 PM

    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)

    Lemke Design+Fabrication
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