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Thread: A4 strength

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    AngusMcDoon's Avatar
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    Default A4 strength

    Is all A4 steel the same strength, or does it come in different grades? I have to replace an M10 bolt, and the application is fairly critical to the integrity of my boat. The old bolt is marked A4 but has no strength indication like good quality rusty steel bolts have.
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    Information on the following suggests stainless bolts are manufactured in different strength grades

    http://www.bssa.org.uk/topics.php?article=1

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    VicS is offline Registered User
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    Default Stainless

    Its 316 St St and it will not have the tensile strength stamped on it. All 316 is made to the same recipe, what is the bolt holding, replace it like for like there is always a factor of safety built into these things.

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    So it looks like A4 does come in different strength grades, but I have no way of telling what grade the bolt to be replaced is. Makes it difficult to replace it like for like. Pity that SS bolts are not marked like rusty steel bolts.

    The bolt attaches a beam hinge to the hull on my Dragonfly trimaran. It's one of 40, 10 per hinge.
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    VicS is offline Registered User
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    Quote Originally Posted by AngusMcDoon View Post
    So it looks like A4 does come in different strength grades, but I have no way of telling what grade the bolt to be replaced is. Makes it difficult to replace it like for like. Pity that SS bolts are not marked like rusty steel bolts.

    The bolt attaches a beam hinge to the hull on my Dragonfly trimaran. It's one of 40, 10 per hinge.
    If its not marked with a grade I think you will find its the lowest.

    heavens knows where you'll buy any of the higher grades

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    Default

    contact manfacturers for spec sheet ?

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    CelebrityScandel is offline Registered User
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    Quote Originally Posted by AngusMcDoon View Post
    Pity that SS bolts are not marked like rusty steel bolts.
    They are so marked - for example, A4 property class 70 bolts will be marked A4-70. If not so marked one can assume they are property class 50.

    But for a critical installation just do as another has advised and ask the builder of the boat in order to be sure what is required.

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    penfold is offline Registered User
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    Quote Originally Posted by CelebrityScandel View Post
    They are so marked - for example, A4 property class 70 bolts will be marked A4-70. If not so marked one can assume they are property class 50.

    But for a critical installation just do as another has advised and ask the builder of the boat in order to be sure what is required.
    Also buy the fasteners from a reputable supplier who can offer some traceability, rather than some bloke off ebay(not that there aren't reputable traders on ebay, just 'caveat emptor').
    Grünkraft? - nein danke.

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    Quote Originally Posted by penfold View Post
    Also buy the fasteners from a reputable supplier who can offer some traceability, rather than some bloke off ebay(not that there aren't reputable traders on ebay, just 'caveat emptor').
    The problem is finding a supplier who will sell just 1 or 2. I have found the part (of unspecified property class) from www.seascrew.com. At least they seem UK based and have a phone number, so I shall call them and try to find out if their products are made to any specification. Thanks for the advice from everyone.
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