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  • Bolt Strength Calculation for lifting

    Discussion in 'Calculations' started by JESSEMK, Sep 18, 2015.

    1. JESSEMK

      JESSEMK New Member

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      Hello I have a Injection mold that is being lifted up by an eye bolt that is mounted on a bridge to locate the eye bolt around a hydraulic cylinder. There is concern that the 4 bolts in the bridge may shear due to the side load caused by the direction the mold is being lifted. The mold weighs 5,900lbs and the bridge bolts are 5/8 socket head cap screws with a total length of 10.5 inches with 1.5 inch of thread engagement. The mold is often rotated 90 degrees and also lifted straight up. Could someone help me calculate if the bridge bolts are strong enough for this type of load or if they will possibly shear.
       
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    3. Benoit Jolin

      Benoit Jolin New Member

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      I would avoid loading in shear through the threaded area. However sometimes it is necessary. You do not specify if the fastener is UNC or UNF nor do you specify the grade of the fastener. These are required to know the cross section area of the fastener and to know the strength of the steel. Then it's a shear calculation based on the tensile strength. Usually I use .75 as my shear strength factor. See machinery's handbook.
       
    4. edleit

      edleit New Member

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      Jesse,

      To avoid loading the bolts in shear, consider installing a set of dowel pins between the lifting fixture and the mold. Providing clearance holes in the fixture for the lifting bolts will allow the pins to take any shear load developed when the clamped fixture/mold are rotated. As Benoit has suggested, fastener grade matters, especially in a situation that involves overhead lifts.

      - Ed
       
    5. Bill @ ERG

      Bill @ ERG Member

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      Your description did not mention the arrangement of the four bolts mounting the bridge, the base width, or the height to the lifting point relative to the base of the bridge (maximum moment arm). In addition to the shear loads, which are quite low for these size of fasteners, the bridge will put some or all of the fasteners into tension when the bridge is lifted to put the fasteners in shear. As mentioned above it may be worth installing dowels - one arrangement is using hardened hollow dowels at two fastener locations if space is at a premium.

      Follow manufacturer recommendations in the application of the lifting eye - side loading is usually derated and mounting arrangement can be critical. Swiveling eyes generally have the best capacity in situations where loading direction changes during hoisting.

      Bill
       

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