Torquing question

Av8torTom · #1 07-23-2011, 01:12 PM

I'm torguing the four AN3 bolts that hold the tie-down plate to the spar. I noticed 10 inch pounds is required to turn the nyloc nut on the bolt. Specs call for 20-25 inch pounds of torque, so I'm continuing until the wrench reads 30-35 inch lbs. (20-25 + 10). Does this sound right? Seems hardly tightened at all. Were I not using a torque wrench I would have tightened it quite a bit more.

Thanks,

Tom

CharlieWaffles · #2 07-23-2011, 01:52 PM

An interesting thing I've learn is that the torque wrench often keeps me from OVER tightening a bolt. As Vans says when you call "it really doesnt take much torque to properly set an AN3 bolt". I tend to think of it as a measured way not to snap the AN3 bolts in half.

Av8torTom · #3 07-23-2011, 02:10 PM

let's hear it for torque seal lacquer. Should know soon enough if things aren't staying put...

Thanks guys

jjconstant · #4 07-23-2011, 03:18 PM

On AN3 bolts/nuts I noticed that when torqued "correctly", I could still rotate the combination of bolt/washer/nut in the hole with a wrench on either the nut or bolt. This is with a calibrated in/lb torque wrench. If I "over-torqued" by another 5 pounds, the assembly would not rotate on its own. I confess to having over-torqued by this amount to prevent rotation of the assembly due to vibration etc. I developed the (bad?) habit of torquing AN3s by tightening just enough to not rotate in the hole. Repeatedly checking shows this as 5lbs over spec.

Is this a problem waiting to rear its ugly head?

Always looking to learn...

Jeremy Constant

Walt · #5 07-23-2011, 04:31 PM

Quote:

Originally Posted by jjconstant

On AN3 bolts/nuts I noticed that when torqued "correctly", I could still rotate the combination of bolt/washer/nut in the hole with a wrench on either the nut or bolt. This is with a calibrated in/lb torque wrench. If I "over-torqued" by another 5 pounds, the assembly would not rotate on its own. I confess to having over-torqued by this amount to prevent rotation of the assembly due to vibration etc. I developed the (bad?) habit of torquing AN3s by tightening just enough to not rotate in the hole. Repeatedly checking shows this as 5lbs over spec.

Is this a problem waiting to rear its ugly head?
Always looking to learn...
Jeremy Constant

I don't think there is anything wrong with this, and in fact, I do it the same way myself most times. You'd be suprised how many bolts I find that are "torqued" with zero clamp up force because the bolt is to long and the "torque" was actually due to it running out of threads.

az_gila · #6 07-23-2011, 05:21 PM

Quote:

Originally Posted by Walt

I don't think there is anything wrong with this, and in fact, I do it the same way myself most times. You'd be suprised how many bolts I find that are "torqued" with zero clamp up force because the bolt is to long and the "torque" was actually due to it running out of threads.

If the extra torque is tightening the joint then you are putting extra stress on the bottom thread of the nut which is not particularly good. A bit more and the threads could deform or the bolt stretch slightly in that spot. Not good assembly practice....

Follow AC 43.13 and add a washer. Then the correct torque will work...

lorne green · #7 07-23-2011, 06:51 PM

Quote:

Originally Posted by Av8torTom

I'm torguing the four AN3 bolts that hold the tie-down plate to the spar. I noticed 10 inch pounds is required to turn the nyloc nut on the bolt. Specs call for 20-25 inch pounds of torque, so I'm continuing until the wrench reads 30-35 inch lbs. (20-25 + 10). Does this sound right? Seems hardly tightened at all. Were I not using a torque wrench I would have tightened it quite a bit more.

Thanks,

Tom

I set my torques for the heavy side of the spec. So, an AN3 would see a torque value of 25 in/lb which would include any torque drag from the AN nut.
I don't see 10 in/lb on every AN nut.
Regards,