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Posted by Desoto61 [138.162.0.46] on Friday, April 13, 2012 at 07:51:37 :
In Reply to: Why all the fine threaded bolts? posted by Wayneh [68.55.55.71] on Friday, April 13, 2012 at 07:32:01 :
From http://www.katonet.com/techinfo/articles/coarse_vs_fine.html
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Reasons to Use Fine Threads:
Fine threaded bolts are stronger than the corresponding coarse threaded bolts of the same hardness. This is in both tension and shear due to the fine threaded bolts having a slightly larger tensile stress area and minor diameter.
Fine threads have less tendency to loosen under vibration due to their having a smaller helix angle than coarse threads. Fine thread Locking Insert grip coils are more flexible than coarse thread insert corresponding size grip coils, and are less likely to take a set under vibration conditions.
Fine threads because of their finer pitch allow for finer adjustments in those applications that need this characteristic.
Fine threads can be more easily tapped into difficult to tap materials, and thin walled sections.
Fine threads require less tightening torque to develop equivalent preloads to the corresponding coarse thread bolt sizes.
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As you've no doubt discovered most of the stuff on these trucks is designed to be heavy duty and handle a life of vibration and hard work.
I would imagine the fact that much of it does not have the metalurgy and technology available today also helped ensure adequate strength.
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