I've heard that bolts should be used for connections that must be secure, rather than welds. To me this seems odd; I was under the impression that the whole idea of a weld was to make the two pieces of metal bond and behave as if they were one piece of metal from the beginning. To me that "sounds" stronger than a method where one must drill a hole clean through a piece of metal in order to attach the bolt.

Why might a weld be weaker?

  • This likely depends on the metals being joined, the thicknesses of the metals, etc. – Tester101 Feb 24 '12 at 19:26
  • This sounds like a Gorilla vs. Shark question. – Tester101 Feb 24 '12 at 19:27
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    This is more mechanical engineering than home improvement. – dbracey Feb 24 '12 at 20:18
  • @Tester101: Trying to remember now but I remember seeing a ton of safety regulations requiring joints (particularly on aircraft, even when the joint is not an aluminum joint) be bolted rather than welded. But I can't remember where at the moment :( – Billy ONeal Feb 24 '12 at 20:58
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    @BillyONeal That may not be because they feel welds are weaker, rather it might be due to repair and maintenance issues. It's a lot easier to remove a damaged part if it's bolted on, than if it's welded. – Tester101 Feb 24 '12 at 21:18

Under perfect conditions this is not true. However most of us are unable to weld something under perfect conditions. There is always the risk of contaminants, imperfect welds, incorrect temperatures, etc.

This holds true even in many industrial factories. For this reason, some very high end cars have their frames glued together instead of welded.

You might have heard this under the assumption that most people don't do a great job at welding and as a result, a bolt is less likely to fail and easier to recommend. Of course this also assumes that the company who made the bolt has good quality control too and they always hold the forces they are supposed to (unlikely in the real world with the typical low quality stuff we buy).

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  • One other issue to note is that for many bolted connection details (although not all) the connection fails in a ductile manner, giving some warning prior to failure. For many bolted connections this is not the case. For critical connections it is not just the plane strength of the connection that is important but also issues like durability and ductility. – Ian Turner Feb 26 '12 at 12:11

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