"How nut torquing and back-off are used to set wheel bearings
How do we adjust wheel bearings to meet the correct end-play specifications? Following is a simple, five-
step procedure:
1.
2.
3.
4.
5.
Torque the adjusting nut to 200 lbf-ft to seat the bearing components. Always rotate or oscillate the wheel while torquing the adjusting nut to ensure that the rollers are fully seated against the cone large rib.
Back off the adjusting nut one full turn or until it’s loose.
This is where you actually establish end play. Torque the adjusting nut to 50 lbf-ft while rotating the wheel hub assembly.
Back off the inner (adjusting) nut the appropriate amount as indicated by the chart at right; e.g., 1/6 of a turn for a 12-threads-per-inch front steer axle. See chart at right for the exact back-off amount. WARNING: Failure to back off the inner nut as described may cause the bearing to run hot and be damaged. If this happens during operation, the wheel also may lock or come off, causing a risk of serious bodily harm.
On a single-nut system, install a cotter pin. On a double-nut system install a jam nut and torque it to the proper specification, which varies depending on the size of the nut."
How nut torquing and back-off are used to set wheel bearings - Timken
http://www.timken.com/pt-br/solutions/automotive/.../techtip...

explication : http://oi43.tinypic.com/5u3fd1.jpg
http://books.google.be/books?isbn=2710806312 - Translate this page
Jean-Paul Nguyen - 1993



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Note added at 7 hrs (2013-08-23 22:05:23 GMT)
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The same physics apply on planes : nuts and bolts need tightening at a certain TORQUE (couple de serrage).

"AIRCRAFT HARDWARE
What You Need To Know
By Ron Alexander
FIGURE 2: AN Aircraft Bolt Dimensions

It is important that you do not "over tighten" or "under tighten" a bolt or the nut attached to a bolt. Under torque or under tightening results in excessive wear of the hardware as well as the parts being held. Over tightening may cause too much stress on the bolt or nut. The best way to avoid this is to use a torque wrench. AC43-13 presents a table of torque values for nuts and bolts. It shows fine thread and coarse thread series with a minimum and maximum torque limit in inch pounds. I recommend using a torque wrench whenever possible, at least until you get an idea as to the amount of force required. Of course, critical installations should definitely be torqued to proper values. A torque wrench is not that expensive and will be a worthwhile investment for a custom builder."
http://www.exp-aircraft.com/library/alexande/hardware.html

"NUMÉRO - Issoire Aviation
http://www.issoire-aviation.fr/doc_avia.../LSIA02RA.pdf‎Translate this page
Un examen des manuels d'entretien des appareils concernés a montré que les couples de serrage des boulons d'hélice indiqués étaient fréquemment erronés.

mehno0102 - DYN'AERO
http://www.dynaero.com/wp-content/.../MEHNO0102.pdf‎Translate this page
Aug 7, 2012 - AUPA (Dyn Aéro) 19, rue de l'aviation 21121 Darois France ( 33 ) 03 80 35 60 62 Fax ( 33 ) 03 80 .... Couple de serrage des vis : M6 = 10 N.m."

"Rapports du BST - Aviation 1999 - A99C0208 - Publications du ...
http://publications.gc.ca/collections/.../TU3-5-99-31F.pdf‎Translate this page
écrous à embase de cylindre du cylindre que l'on remplace; il faut également vérifier le couple de serrage du cylindre opposé qui partage les mêmes boulons ..."