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Guides for bolt diameter and length against plate thickness?

  1. May 15, 2015 #1
    I tried to find design regulations/codes that specify relations between bolt diameter/bolt length against connected plate thicknesses. I couldn't find that in Eurocodes 3. Can someone help me with info where to find those regulations ?

    Example: can we connect 5 mm plates using M24 ? or vise versa, i.e. connect 32 mm plates with M8 ?
    what about bolt length ?,
    is there any helpful regulations to go through ?
    Thanks in advance.
  2. jcsd
  3. May 15, 2015 #2


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    Hello Raf76, Welcome to PF.

    You can connect any plates with any size bolts, because you did not specify a load that tries to push, split or tear the two plates apart.
    As far as I know there are no regulations on sizes, but on the loads that need to be supported by said plates and bolts.
    A diagram of your intended setup and some sizes could be useful.
  4. May 18, 2015 #3


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    Gold Member

    Hello, Raf. There is a British/EU Standard for bolted connections in structural design which might be useful:
  5. May 18, 2015 #4
    Thank you for your reply.
    I have reached the same answer you proposed after many hours of searching. But one of my friends has advised as a rule of thumb, he said, to use the same plate thickness as bolt diameter or something nearby. As example to connect 12 mm plates with M12. It could be logical!.
    By precise case is that I wanted to connect two steel beams together using bolts. Big beam which is a part of platform HEB700 with flange thickness of 32 mm and the small beam is HEB140 with flange thickness of 12 mm. This small one is a cantilever (i.e. connected only to HEB700) and carrying some 0.5 KN on three directions at the free end of it.
    The question here was the choice of the bolt diameter. Regards.
  6. May 18, 2015 #5
    Thanks tech99
  7. May 18, 2015 #6


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    In this case there are regulations. Mostly there is a maximal accepted hole that you can drill in the HEB140 before it loses it's structural properties. Why not make that your bolt diameter? As the biggest is clearly the best.
    The Mechanical and Metal Trades Handbook (aka "the BIBLE" for all but the meaning of life) tells us of a maximal hole diameter of 21mm (For an IPB140 as designated in the "DIN 1025-2 (1995-11)". So a M20 sounds nice. And the other HEB 700 will not care.
  8. May 18, 2015 #7
    Thanks for your reply.
    I have checked and will use your advice. :)
    Kind regards.
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