Posted by Clint Dixon [172.68.90.97] on Thursday, May 17, 2018 at 10:10:29 :
In Reply to: Re: U-bolts revisited posted by Daryl in Oz [162.158.2.19] on Wednesday, May 16, 2018 at 21:17:33 :
I find it interesting that so many of the sites "blame" the deep nut for distorting the threads on the u-bolts. There is nothing special about a deep nut other than a longer length with more thread engagement - unless the deep nut has cut threads in comparison to the u-bolts rolled threads. If that is the case it is not surprising that threads are distorting. Probably those in the nut are distorting more than those on the u-bolt as the rolled u-bolt threads would be stronger than the cut threads in the nut.
This all points to it being done on purpose. And the only engineering reason I can think of for it being done on purpose would be to create a sort of "lock" between the threads once they are torqued.
If a nut is backed off after being torqued and it does not spin as freely coming off as it did going on, then there has definitely some thread damage that has taken place. I have removed nuts from original u-bolts after cleaning the threads and they have spun off easily once loosened. I also found out that the torque specified in the shop manual for u-bolt nuts on the WDX or B1PW was about 65 lb. max. (I will look again to confirm). This is not really all that much for that size of thread.
Junior
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