Torquing AN3 bolts

[prkaye]

I was installing bolting the inbaord hinge-bracket/bearing assembly to the rear spar of the HS today. The plans called for AN3-5A bolts, AN960-10 washers and AN365-1032 nuts.
These parts weren't labelled explicitly in the stuff from Vans, but there was a bag which was labelled in the parts list as "AN3 Hardware". Inside I found bolts washers and nuts. I verified the bolts to be AN3 with my bolt gauge and selected ones with a length of 5.
Questions:

1) Were these the right bolts? What does the final "A" mean an AN3-5A ?

2) The nuts in the bag were all identical, they all had white plastic inserts in them. Are these the AN365-1032 nuts?

So I went ahead and used these parts. I set my torque wrench for 20in-lbs, and began to tighten them. The torque wrench never released (although I've never used a torque wrench so I'm only guessing what this would feel like. What happened was that the nuts eventually got to a point where they turned sort of freely, without tightening on the bolt anymore. This made me wonder...

3) Do these nuts somehow self-torque with those plastic inserts? Should I be worried that they stopped tightening before 20 in-lbs, when the guidelines say AN3 bolts should be torqued to 20-25 in-lbs?

If I'm correct in my hypothesis about the nuts self-torquing, one more question...

4) How much damage to those nuts can result if I keep turning them once they have stopped tightening? Should I replace them?

Thanks!

Phil

[jlfernan]

I can't help you with the ID of those bolts except that the "A" indicates the bolt is not drilled for a cotter pin, but I can offer some advice. IMHO when in doubt, redo it. Bolts are cheap and it's worth the piece of mind. When it come to torque wrenches, I posted this several times. Grainger.com sells a dial type torque wrench made by Proto. All you have to do is look at the dial and you know what the torque is. I would not trust my ears to hear a "click" from a standard wrench, when you are dealing with the low torque settings in the airplanes, it may not "click". When you set the torque you must factor in torque drag. That's created by the friction between the bolt and the nylock nut or nutplate. This amount is to be added to the torque specified for the particular hardware you're using. It's figured by running the nut down to where it almost touches the surface. The Proto wrench I use, has a blue needle which you set to zero. Turn the nut about a half turn and see where the blue needle stops, the nut should still not be tight to the surface. Then add that that amount to the torque spec
ie; 20-25in lbs + 5in lbs=25-30in lbs. I'm not sure what you mean about the nut stop tightening. It should tighten at and beyond the torque setting. These bolts are not "self-torquing". The plastic insert only serves to keep the nut from backing out. Also mark your torqued bolts with torque seal so that during you inspections you can confirm your bolts haven't loosened.

[OneTwoSierra]

Originally Posted by prkaye

I was installing bolting the inbaord hinge-bracket/bearing assembly to the rear spar of the HS today. The plans called for AN3-5A bolts, AN960-10 washers and AN365-1032 nuts.
These parts weren't labelled explicitly in the stuff from Vans, but there was a bag which was labelled in the parts list as "AN3 Hardware". Inside I found bolts washers and nuts. I verified the bolts to be AN3 with my bolt gauge and selected ones with a length of 5.
Questions:

1) Were these the right bolts? What does the final "A" mean an AN3-5A ?

2) The nuts in the bag were all identical, they all had white plastic inserts in them. Are these the AN365-1032 nuts?

So I went ahead and used these parts. I set my torque wrench for 20in-lbs, and began to tighten them. The torque wrench never released (although I've never used a torque wrench so I'm only guessing what this would feel like. What happened was that the nuts eventually got to a point where they turned sort of freely, without tightening on the bolt anymore. This made me wonder...

3) Do these nuts somehow self-torque with those plastic inserts? Should I be worried that they stopped tightening before 20 in-lbs, when the guidelines say AN3 bolts should be torqued to 20-25 in-lbs?

If I'm correct in my hypothesis about the nuts self-torquing, one more question...

4) How much damage to those nuts can result if I keep turning them once they have stopped tightening? Should I replace them?

Thanks!

Phil

The A is a hole-less (non-drilled) bolt (no provision for a cotter pin).
AN365-1032 nuts have different colored inserts depending on the manufacturer. They are a 3/16 nyloc nut. Nothing self torques. You've destroyed the nuts and bolts. Please get someone to help you.

[rvbuilder2002]

Before you get to far I would suggest you read through chapter Five of your construction manual.
I may be mistaken, but I believe it has all the information you need for hardware identification.

[DanH]

Phil,
The "A" suffix means "undrilled", as in no hole for a cotter key.

We can't tell what nuts were in the bag, but you can. Fiberlock nuts come in thin for shear applications (AN364) and thick for tension applications (AN365). You MUST learn to identify the difference on sight. Lacking a better reference, you could consult an Aircraft Spruce or Wicks catalog and look at the pictures.

If you used an AN364 shear nut and tried to torque it to 20 in-lbs, the threads on the bolt or in the nut will be damaged.

I assume you have a click-type torque wrench. It does not "release". It makes a little click, thus the name. If you pulled past the click, the threads are likely stripped.

Regardless, if the nuts are turning freely now, you need to remove them for a close inspection of the bolt and nut threads. If they are not perfect throw them away.

Nuts DO NOT "self torque".

Strongly suggest that you find a local TC, licensed mechanic, or experienced builder for some school on very basic shop issues. Guessing about aircraft hardware and its proper installation is a bad thing.

Dan Horton

[jlfernan]

How much should you torque a AN364 nut? Everything I've read does not indicate diffference in torque between 364 or 365 nuts.

[prkaye]

I just tried my torque wrench (Power Fist 1/4" drive torque wrench) on a spare nut and bolt just to get the feel for it... I wonder if it's not working. I tightened very hard, and no clicking, nothing discernable happens.
I wonder if it's because I got it for less than $30 (CAD) ?

How much should I spend for a suitable wrench? Do I want 3/8" drive or 1/4" drive?

Is this one overkill?

http://www.grainger.com/Grainger/wwg...mId=1611691126
(it's $184 USD).

[LettersFromFlyoverCountry]

I have a Craftsman torque wrench. It doesn't click per se so hearing it , ummm,, not click...isn't a problem.

But it "gives" a bit when it reaches the proper torque. It's kinda impossible not to feel it.

AC 43-13 is your friend.
One other thing I'd recommend. Get all your hardware out of the bags as soon as possi ble after they arrive and sort them all out into stackable bins you can buy at Ace or any other hardware store.

I also add 365 nuts and the more common bolts and washers to the order every time I make one with Aircraft Spruce or whomever. That way there's no reason not to toss a bunch of 'em in the trash if I've used them.

[mlw450802]

Phil,
Read this thread for more info.
http://www.vansairforce.com/communit...=torque+wrench

-mike

[prkaye]

A related question, how do i remove those damaged self-locking nuts so I can re-do this properly?