is there any negative effect to accuracy if the nut torques up at the higher end of the range?..
Printable View
is there any negative effect to accuracy if the nut torques up at the higher end of the range?..
Over torquing can cause deformation and failure of the threads. In this case, there's probably a little extra room to go over a little, but not something I'd want to put to the test.
Ideally, torque should be set to nominal; that is, the middle of the torque range. In this case, that is not only difficult to achieve but also isn't the goal. For the most part, keeping within the torque range shouldn't be difficult to do as that's how the parts are engineered to fit. Some over think it. They'll torque to the minimum (which if I recall right is 35 ft/lbs) but will continue without checking to see if everything lines up. Torque it to the minimum first, using the proper technique and check it. If it lines up, your'e done!
If the assembler cannot get the notch to line up between the minimum and maximum, the assembler should stop and re-evaluate the technique used. The barrel nut is system is engineered to line up within the torque range. Some don't realize they need to compensate for the extra arm of the barrel nut tool. When starting, they set the torque wrench to 35 but unless the arm is compensated for, they actual torque will be greater and the notch torqued past where it should be. Torquing to the next notch means they go too far and too much torque is needed. I think too that many assemblers don't reach a high enough torque during the first two tightenings and the parts don't set properly before the final torque.
Set the barrel nut tool 90 degrees to the torque wrench, set the wrench to the upper end of the torque range, torque and loosen two or three times. Then set the wrench to the minimum, torque and check alignment. If it's there, use it! If not, set the wrench to maximum torque and slowly tighten until either the next notch lines up or maximum torque is achieved. If it reaches max torque, loosen and start over. Torque again to the minimum setting and see how close it lines up. Maybe it real close and you just over tightened by a pound or two. Sometimes you just gotta know when it's good enough and accept it*
*What does "good enough" mean? It means it's within acceptable limits. If the notch lines up at the minimum torque it's good enough. If it lines up at the maximum, it's good enough. Both are within acceptable limits
Why set the barrel nut wrench 90 degrees to the tq wrench? If I under stand you correctly. The nut wrench and tq wrench should form a L
a^2+b^2=c^2 ... pythagor..... Former math teacher I digress...
Basically if you place it at a 90 you are much closer to the actual length of your lever(handle) in relation to the torque setting on the wrench, if you are adding a couple inches to the end of the wrench you are increasing that percentage to (for simplistic sake though there are several other factors to account for: ex add 2" standoff between barrel nut pivot point and torque wrench pivot point to a 10 inch wrench 2/10 = + 20% the torque setting; 70 ft lb becomes 84 ft/lb) hence the over torque.
As others have stated its such a broad range between 30-80 ft/lbs if it doesn't line up before you hit 80 chances are you're missing something.
I though that was it. This is why I use a crows foot when working on cars if socket will not work. I do wonder if they make a crows foot for a barrel nut if not easy to make one from a armorers wrench.
I believe what he is saying in laymens terms, rotating the wrench 90 degrees changes the area or point of moment of torque where as keeping the wrench straight with the torque wrench you are increasing leverage increasing the moment of torque. I have heard this before I did my first build and did that this time as well.
Too much thinking happening here.