How to Torque Lock nuts

N537TM · Post by **N537TM** » Fri Mar 24, 2006 12:55 pm

We are getting ready to do some final Torquing of nuts on some areas in the wing.... if they are Lock nuts or bolts going into lock nut plates, how does one set the torque on the wrench???

Mike B.

cjensen · Post by **cjensen** » Fri Mar 24, 2006 12:59 pm

use the chart in the aircraft standards handbook for the size of nut and bolt, make sure to add the torque from the nut drag. easiest with a dial type torque wrench. you just read the nut drag directly, and add that value to the final torque value in the chart.

e.g. i just torqued my tie downs. the nut drag registered 7 in-lbs. the range for the 10-32 nut is 20-25 in-lbs. so, i used 30 in-lbs as a final value (7 + mid-range value of 23 = 30).

hope that helps.

N537TM · Post by **N537TM** » Sat Mar 25, 2006 8:46 am

So just add that drag from the bolt / screw as it nears the botom of the travel.... We have a "Click " type wrench .... so I could find the amount then add it to the total...

That works

Mike

cjensen · Post by **cjensen** » Sat Mar 25, 2006 10:00 am

yeah, clicker types work, but they are trial an error. set it as lite as it will go, and proceed from there. you probably knew that much though!

that's it!

captain_john · Post by **captain_john** » Sat Mar 25, 2006 12:37 pm

The inherent "problem" with torquing a fastener the way we do is that we are measuring a by product.

The thing we want to gauge is fastener tension. That is, in this case... bolt stretch. There is no way to do this in a practical fashion because the fastener is installed in aluminum. How are ya gonna see if it is stretched enough?

You measure the rotational force applied to it. With all things being "standard" (lubricity, free of dirt and debris) it should be consistent and accurate.

We are building a plane that isn't in a laboratory and the environment isn't textbook. Staying as close to the intention of the "standard" is the best we can hope for.

CJ

jim_geo · Post by **jim_geo** » Sat Mar 25, 2006 1:22 pm

We are building a plane that isn't in a laboratory and the environment isn't textbook. Staying as close to the intention of the "standard" is the best we can hope for.

John you are exactly right about that. While talking with many people, mostly non pilot non builder types, I get the impression that a good number of people think that we aircraft builders must be working with some impossible tolerances. Looking at our torque chart all of our bolts have a range. In practice I choose a torque that puts me mid range on the charted torque for a particular bolt. But at either extreme the torque would be just right. I don't know this for sure but it is my suspicion that the nyloc nuts are designed to allow for less grip as the nut is turned over the end of the bolt and develop a tighter grip as the nut is coming to torque.

TomNativeNewYorker · Post by **TomNativeNewYorker** » Sat Mar 25, 2006 4:27 pm

jim_geo wrote: Looking at our torque chart all of our bolts have a range. In practice I choose a torque that puts me mid range on the charted torque for a particular bolt. But at either extreme the torque would be just right.

I was taught on fasteners requiring torque, if torquing from the head side to go to the high end of torque value; nut side - mid to upper value, and for castle/castlelated nuts requiring cotter pins or safety wire to torque to the low end of the value, then tighten if needed to line up cotterpin hole.

As far as nyloc is concerned, we dont use at al so am not really familar with them.

jim_geo · Post by **jim_geo** » Sat Mar 25, 2006 5:16 pm

Tom I was taught to strongly avoid tightening from the bolt side and if need be use torque wrench attachments and recalculate the torque in order to torque from the nut side. I don't know much about it but the shank has always seemed an unreliable and variable source of drag.

TomNativeNewYorker · Post by **TomNativeNewYorker** » Sat Mar 25, 2006 8:20 pm

jim_geo wrote:Tom I was taught to strongly avoid tightening from the bolt side and if need be use torque wrench attachments and recalculate the torque in order to torque from the nut side. I don't know much about it but the shank has always seemed an unreliable and variable source of drag.

Same here, but some cases it just cant be avoided and it must be on the head side. Thus the high end of the value is used.

jlfernan · Post by **jlfernan** » Sun Sep 24, 2006 7:56 pm

In my opinion, a dial type torque wrench is much easier to use. No listening for a click, just look at the dial and you know exactly where you are at.