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Thread: Bolt with 4.8 written on it.

  1. 30th April 2009, 07:36 AM #1
    Aaron
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    Bolt with 4.8 written on it.

    Ive got two bolts, both with 4.8 on the top. Are these concidered high tensile?
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  2. 30th April 2009, 07:39 AM #2
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    Nope .... normal structural grade. You need 8.8 for high strength.
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  3. 30th April 2009, 07:46 AM #3
    Aaron
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    I thought so. Here is the situation.

    About a year ago I bought two of those 10000pung recovery hooks, at the same place at the same time. Yesterday I removed one to do something. The bolts on the one I removed are both 4.8. The other one has 8.8's.
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  4. 30th April 2009, 07:51 AM #4
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    Rosco
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    Most likely 4.8 are the wrong bolt as the threaded area is probably within the shear plane.

    Check out

    http://www.saisc.co.za/cms/files/Cha...%20Bolting.pdf
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  5. 30th April 2009, 06:33 PM #5
    Dougal
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    Don't worry, those hooks will open out before you get near the shear strength of even mild steel bolts.
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  6. 30th April 2009, 08:54 PM #6
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    Rosco
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    Quote Originally Posted by Dougal View Post
    Don't worry, those hooks will open out before you get near the shear strength of even mild steel bolts.
    Possibly even more relevant is the thickness of the steel to which they are bolted. If it's your typical 3-4mm, that is the component which will most likely fail in bearing.
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  7. 1st May 2009, 04:45 AM #7
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    Blknight.aus
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    in the world of proper nut and boltery....

    4.8 is somewhere between toe jam and peanut paste for strength

    8.8 is your nominal strength bolt and (3 radiating lines for imperial)

    10.9 is usually regarded as high tensile. (6 radiating lines for imperial)

    Yes there are other grades out there but when its a marked bolt for automotive use its either 8.8 or 10.9
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  8. 1st May 2009, 05:05 AM #8
    Dougal
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    Quote Originally Posted by Rosco View Post
    Possibly even more relevant is the thickness of the steel to which they are bolted. If it's your typical 3-4mm, that is the component which will most likely fail in bearing.
    Definitely.
    A mate picked up an Isuzu bighorn (holden jackaroo for you aussies) and we're looking to put some better hooks on it.
    The original hooks screw into two nuts welded inside the chassis rails. The rails are maybe 2-3mm thick and it's closed so we can't get anything else in to reinforce it.

    I've heard stories of people installing "rated" hooks to these mounts with grade 8.8 bolts and passing club inspections. Only to have them rip out later.
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