AN3 Torque ?

[Concorde]

The true value for AN 3, 3/16"is supposed to be 25 in/lbs + maybe extra 5 for the nylon fitting .
My problem is that I don't feel comfortable with this ,it's almost like hand tightening the nut.
Some say that it has to be 25 or very close to that and others say that you just need a snug fit and don't really need to worry about it , and I admit that I like the snug fit a lot better but the snug fit to me after working on heavy equipment all my life maybe way too much .
What do you guys think ? Does anyone else feel the same ?

[Sonerai13]

Everybody tends to over-torque all fasteners. This is especially true of smaller stuff like AN-3. The torque tables don't lie. Resist the temptation to tighten it "just a little more".

[n982sx]

I've measured the run on torque of the AN3 nyloc nuts and it is pretty consistently 7 in/lbs. I use 32 in/lbs for these and they stay snug. If you can hand tighten an AN3 nyloc nut, the insert may be faulty.

[Concorde]

Everybody tends to over-torque all fasteners. This is especially true of smaller stuff like AN-3. The torque tables don't lie. Resist the temptation to tighten it "just a little more".

Thanks You Joe . I will do my best not to over torque. I may need to buy better torque ranch.
Ben

[Concorde]

I've measured the run on torque of the AN3 nyloc nuts and it is pretty consistently 7 in/lbs. I use 32 in/lbs for these and they stay snug. If you can hand tighten an AN3 nyloc nut, the insert may be faulty.

Bob, No I can't hand tighten the nut .Lol :mrgreen: I will try 32.
Thanks
Ben

[achesos]

Mr. Norris is correct of course, but I'd like to heighten the message that torque tables are critical to follow. Bolted joints is a science in itself.
The torque required to overcome the nylon locking friction is typically called 'prevailing torque'. This is often measured during joint development in R&D and needs to be factored in to understand the the actual bolt stretch that occurs when the joint tightens. What normally keeps a bolted joint tight is the spring tension of the properly torqued fastener. The screw actually stretches (like a spring) and keeps all the mated surfaces locked together. Another thing that influences prevailing torque is if the threads are lubricated with thread lock or anti-seize. This allows the screw to get more stretch for the same amount of torque applied, which can place the fastener much closer (or beyond to failure) to its safety limit. The torque spec is derived by statistically tightening the same joint multiple times until the screw fails, and recording the torque required to do so - the max allowed torque will be around 65% -75% of this average value to allow for variations in the assembled joint and rate of applied torque or wrench calibration. The short answer here is that 'a little extra' might actually put the screw so close to the working limit that it will fail once a dynamic load is applied to the joint. This must be avoided in aircraft.
Hope this helps.

[SvingenB]

AN bolts are torqued to about 20-30% of "normal" bolts. One may only wonder why, but the effect is that they are not ordinary bolted joints. More like a combination of bolts and shear pins.

[pfhoeycfi]

Can anyone recommend a torque wrench or wrenches? I'm having a little difficulty locating one for the smaller sizes, ie the AN3.

Also curious as to the torque reference tables being used. Found a few...FAA, one on VANs...

Thank you,

Peter
SNB0021 in the works

[Bryan Cotton]

I have an old Sears in-lb torque wrench. Its range is 25-250 in-lb. Home Depot has this:
https://www.homedepot.com/p/Husky-1-4-i ... /206743985
Harbor Freight has this:
https://m.harborfreight.com/14-in-drive ... 61277.html
They are out there.
I have the Van's table on my phone. There is nothing wrong with AC43.13 either.

[Sonerai13]

I use the torque table in AC 43.13 for my AN fasteners.

The torque wrench I have for the small stuff is a Snap-On. I have two actually. One is for really small stuff, 10 to 50 in/lb. The other goes from, I think, 40 to 250 in/lb.