torque and threaded holes w/o nuts

[tomhanaway]

I understand the inch lb. values for bolts and nuts given for AN bolts w/ nuts given in Section 5 of Van's.

Is there a difference in value when AN bolt is going into a threaded hole (no nut)? Seems like the additional resistance of the threads would change the value. If so, is a torque value source available?

Thanks,
Tom H.

[jlfernan]

Before you torque any nut or bolt you need to determine the drag torque, this is caused from the friction created between the bolt and the nut. You then add this amount to the torque value for the particular bolt you are working with. To determine this amount you need to run the nut all the way down to just before it makes contact with either the washer and any surface you will be bolting down. I use a dial type torque wrench, using a click type wrench makes this more difficult. Zero the gauge on the torque wrench(dial type only), turn the nut a small amount. The amount of force displayed on the gauge, is the drag torque. AN-3's are about 5 in.lb. Hope this makes sense.

[az_gila]

Originally Posted by tomhanaway

I understand the inch lb. values for bolts and nuts given for AN bolts w/ nuts given in Section 5 of Van's.

Is there a difference in value when AN bolt is going into a threaded hole (no nut)? Seems like the additional resistance of the threads would change the value. If so, is a torque value source available?

Thanks,
Tom H.

Tom... the results would be material dependant... torque into aluminum would be way less than the torque into steel.

In general, threads into aluminum would be coarse rather than the fine threads of our AN bolts...

Do our RVs have any of these that need torquing? ...the only ones I can think of at this time are the tie-downs and some trim hold down under the horizontal.

Perhaps a very gentle torque and a drop of medium locktite would be a better solution than your torque wrench? -- especially if they are threads we cut ourselves...

gil A

[lrfrey]

I have found that the additional resistance (nylock nuts for example) can usually be accounted for by just using the high side of the spec. It's impractical to measure every fastener, every time.

Like Gil, I can't think of many bolt into thread applications on RV's either, other than on the Engine or Prop and a few large nutplates.

For nutplates under 1/4" I tighten until they stop, then just a 1/8 th of a turn more maybe. These are Phillips and I don't use a torque wrench at all.

For Prop bolt's, I do measure the drag then torque accordingly. For the Engine baffle bolt's (1/4" Phillips) , Case bolt's etc I just torqued to the high spec. Just my approach.

Larry

[tomhanaway]

Ok thanks all.
I was actually looking at the Tru Trak servo in the wing. Not part of the original Van's parts.

As suggested, I'm also a big fan of generic loctite blue when in doubt.

Tom

[RScott]

Jorge describes the correct procedure as is described in AC 43.13 on page 7-6, para 7-40c.

I found quite a bit of variation in torquing the bolts going into the nutplates on the wing spar, so a general rule of tightening 1/8 turn after bottoming out or doing it by feel won't give the correct value. It may feel good, but it's wrong.

You don't have to use a dial type torque wrench, which is generally expensive, although they sometimes can be had cheaply on Ebay. You can use a beam type wrench, although these are not easy to find. However, I bought a Park TW-1, which measures 0-60 inch pounds for less than $33. They are regularly on Ebay for about $35 plus about $8 shipping. This torque wrench is sold to bicycle shops and you may find one locally, but they seem to always be available on Ebay.

It's interesting that we fret over whether this rivet is OK or whether that was done right, but then on other things we say "that looks good enough" and move on. Human nature, I guess and I suspect we all do it.

Richard Scott
RV-9A Fuselage