AN3 Torque ?
Posted: Fri Jul 03, 2015 2:16 pm
by 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 ?
Re: AN3 Torque ?
Posted: Fri Jul 03, 2015 2:39 pm
by 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”.
Re: AN3 Torque ?
Posted: Sat Jul 04, 2015 3:13 pm
by 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.
Re: AN3 Torque ?
Posted: Sat Jul 04, 2015 7:20 pm
by Concorde
Sonerai13 wrote: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
Re: AN3 Torque ?
Posted: Sat Jul 04, 2015 7:26 pm
by Concorde
n982sx wrote: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
Re: AN3 Torque ?
Posted: Tue Sep 22, 2015 10:12 pm
by 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.
Re: AN3 Torque ?
Posted: Wed Sep 23, 2015 1:20 am
by 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.
Re: AN3 Torque ?
Posted: Tue Jul 10, 2018 3:12 pm
by 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
Re: AN3 Torque ?
Posted: Tue Jul 10, 2018 7:59 pm
by 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.
Re: AN3 Torque ?
Posted: Wed Jul 11, 2018 9:11 am
by 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.
Re: AN3 Torque ?
Posted: Wed Jul 11, 2018 10:50 am
by EdW
Remember, torque wrenches are precision measurement tools, and as such require periodic calibration. In certificated operation, 24 months is limit. How do wrenches get out of tolerance? Usage, dropping, usage, dropping, etc. Like the rest of us, they wear out.
Ed
Onex 209
tailwheel, Aerovee
Nobody here liked the name I selected for my bird, so I am changing it to DILLIGAS.
Just east of Graceland
Re: AN3 Torque ?
Posted: Wed Jul 11, 2018 11:28 am
by dallen
Sonerai13 wrote: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.
Joe, Could you post “AC 43.13”. I would like to see it.
Dave
Onex
Re: AN3 Torque ?
Posted: Wed Jul 11, 2018 12:24 pm
by DCASonex
Another place to look for small torque wrenches is gun smith supplies. For AN3 and smaller, I have a small one that looks like a fat screw diver, very good for small places, and quick and easy to use. Be sure to check calibration. If no other known accurate wrench available, use a simple torque arm and weight.
David A.
Re: AN3 Torque ?
Posted: Wed Jul 11, 2018 2:12 pm
by Bryan Cotton
dallen wrote:Joe, Could you post “AC 43.13”. I would like to see it.
Dave
Onex
Google can find it for you. You want to download the hardware chapter. It is an FAA document.
Re: AN3 Torque ?
Posted: Thu Jul 12, 2018 11:01 am
by dallen
Got it thanks.
Dave
Re: AN3 Torque ?
Posted: Thu Jul 12, 2018 12:10 pm
by radfordc
DCASonex wrote:Be sure to check calibration. If no other known accurate wrench available, use a simple torque arm and weight.
David A.
Here is a video of how I calibrate a torque wrench… https://youtu.be/jdhFqpLJKT8
This was a presentation made at one of the Midwest Sonex Fly-in’s several years ago.
Re: AN3 Torque ?
Posted: Fri Jul 13, 2018 10:17 am
by Sonerai13
dallen wrote:Joe, Could you post “AC 43.13”. I would like to see it.
http://www.marvgolden.com/downloads/dl/ … xcerpt.pdf
A web search will find other similar links.
Re: AN3 Torque ?
Posted: Tue Jul 17, 2018 6:43 pm
by pfhoeycfi
DCASonex wrote:Be sure to check calibration. If no other known accurate wrench available, use a simple torque arm and weight.
David A.
Thanks for those responses… ended up with a Capri, did the wight x arm test and it was right on…
Thank you,
peter