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Shear strength of bolts, check me on this.....

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  • old mart
    replied
    They wouldn't have broken if they had been done up properly. 8.8 bolts are medium strength, the 10.9 and 12.9 are stronger.

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  • reggie_obe
    replied
    Be easier to look up the press specs. Model 200b, 22s, 2a, 20c, ??

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  • The Metal Butcher
    replied
    Originally posted by DR View Post

    There's only maybe .030" play in the table when the bolts are loose so they all sheared very close to the same time. What is a little puzzling is why the bolts don't shear when tightened up with the same die set mounted as when they sheared.
    I don't have the time to check the number right now, but I can answer the second.

    Except in specially designed shear bolts, meant to fail, bolts should never be loaded in shear. Instead, the tremendous tensile force they can create holds items together via friction. In a bolted joint say on a beam, zero percent of the load should be handled by the bolt in shear. This is why it is important to torque bolts in such a load case to their specified value.

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  • DR
    replied
    Originally posted by kendall View Post
    Assuming the bolts all sheered at once, I'd say there's a good chance.
    There's only maybe .030" play in the table when the bolts are loose so they all sheared very close to the same time. What is a little puzzling is why the bolts don't shear when tightened up with the same die set mounted as when they sheared.

    Leave a comment:


  • kendall
    replied
    Assuming the bolts all sheered at once, I'd say there's a good chance.

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  • DR
    started a topic Shear strength of bolts, check me on this.....

    Shear strength of bolts, check me on this.....

    My Perkins horn type punch press has a height adjustable table. I need to know the rated tonnage of this punch press.

    The table has four 5/8" grade 8 bolts holding it in position. While setting up the press the bolts were mistakenly not tightened leaving the table with some looseness. The press was stroked with the table loose shearing off all four bolts in their threaded area. Googling tells me the shear strength of the bolts are 30kn each in the threaded area. Converting to pounds force equals 3.35 tons, times 4 equals 13.4 tons.

    So, is it fair to assume the tonnage of this press is at least 13 tons?

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