View single post by atgparker
 Posted: 08-11-2013 02:48 pm
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atgparker



Joined: 06-23-2013
Location: Mission Viejo, California USA
Posts: 78
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I used to work on wind mills back in the 80's. We used a lot of F911 (better than grade 8) fasteners for mounting the blades to the hubs. When we applied Loctite to the fasteners we always reduced the torque by ten to fifteen percent. This was a rule of thumb so if you really want to get to the crux of things you need to mount a 7/16-20 bolt in a rugged steel sleeve, nut it, hand tighten and measure the OAL of the bolt with a micrometer. The bolts length does not need to be the same length as the wheel stud in fact if its longer and the micrometer has the reach it will be a bit more sensitive. Torque it to 51 ft./lbs. and measure the OAL again and subtract the initial value to get the elongation. Then take a second bolt and never seize it up and measure it. Then torque it up in increments until you achieve the same elongation as the other bolt that was with out the lubricant on it. That torque that you arrive at should be the proper torque with the never seize on the threads. As the JH OEM lugs are aluminum I would be careful not to go gonzo with this as a 3/4 or 19mm hex usually lives on a 1/2-13UNC or 1/2-20UNF bolt or screw. On this size fastener when all in steel 75 ft./lbs. (with Loctite) is a proper torque for fixing a grade 8 fastener, dry it is 110 ft./lbs. But the aluminum lug nut has 1/3 the modulus of its steel wheel stud counterpart. Recommendations for dry steel on steel threads in 7/16-20 at grade 2 is 41 ft./lbs., grade 5 is 57 ft./lbs., and grade 8 is 70 ft./lbs. While the tensile qualities of the stud are easily in the grade 8 range the nut is not. So I would be looking to fix my JH aluminum lug nuts with never seize to a torque of 35 to 40 ft./lbs. The important thing is that with only four of them that they be tightened to the same amount as is physically possible with a good quality 3/8 drive torque wrench. I think this size tool will be better than a 1/2 inch drive one for the torque we are looking to produce.