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How much torque on these fittings?

swisseagle

Well Known Member
Hello,

I know, many times asked here, but no precise answer ...

The Aeroquip aluminum fittings use this table: http://vansaircraft.com/pdf/Torque_Spec_Aluminum_Fittings.pdf
The aluminum tube to AN fitting use this table: AC 43.13-1B / TABLE 9-2. Tube data

But what the heck should I use on these, engine fuel pump fitting on the o-ring jam-nut:
cat-med_pump-fittings.jpg


Thank you for any input!
 
Lycoming SSP-1776-B (Revision B) has a torque table for Straight Thread O-Ring Boss Fittings, which is exactly what these fuel pump fittings are called.

For a tube size of AN6 using a 9/16-18 thread, the torque is 23-24 ft-lbs.

lycoming-torques_zpsd981c236.jpg


Edit: Rev B is really hard to find. Gil (az_gila) posted this copy on another thread.
 
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Lycoming SSP-1776-B (Revision B) has a torque table for Straight Thread O-Ring Boss Fittings, which is exactly what these fuel pump fittings are called.

For a tube size of AN6 using a 9/16-18 thread, the torque is 23-24 ft-lbs.

lycoming-torques_zpsd981c236.jpg


Edit: Rev B is really hard to find. Gil (az_gila) posted this copy on another thread.

What is table 1 for? I made a mistake some time back thinking that the "10" refers to -10 nut/bolt with torque of 49.
Thanks.
Johan
 
Threads...

I just had the same question. Didn't know that these fittings were "straight thread".
What makes thread "straight" or "non-straight"?:confused:
 
I just had the same question. Didn't know that these fittings were "straight thread".
What makes thread "straight" or "non-straight"?:confused:

In this case "straight thread" is used to identify fittings that are not a tapered "pipe thread".
 
What is table 1 for? I made a mistake some time back thinking that the "10" refers to -10 nut/bolt with torque of 49.
Thanks.
Johan

Table I is the general torque for nuts on a Lycoming engine.

"10", being listed before "1/4" is a reference to #10 screws/bolts which are essentially 3/16 inch diameter.

The Lycoming bolts are almost all coarse thread and the torques are specified for oiled threads, rather than the dry thread specifications used for airframe bolts.
 
In this case "straight thread" is used to identify fittings that are not a tapered "pipe thread".

Gil,
Referring to table 1, does the "10" in the "thread" column refer to -10 (AN3) nuts and bolts, or threads per distance (pitch)? The next numbers down led me to believe that it refers to bold/nut diameter and not threads per distance. That is my confusion in reading this sheet. The correct torque for AN3 is 20-25 inch.lb. Where does the 49 come from?
Thanks.
Johan

PS. We posted at the same time!!
I assume that the table does not apply to AN3 1032 nuts and bolts threads??
Does the coarse threads take a much higher torque than finer threads?
 
Last edited:
Gil,
......
I assume that the table does not apply to AN3 1032 nuts and bolts threads??
Does the coarse threads take a much higher torque than finer threads?

Yes, the coarse threads can take more torque, but in this case it's simply a matter of following the manufacturer's requirements.

Torque required is related to thread, lock washers, friction (the oiled bit) and material the bolt is made from.

In this case, I can't remember any 10-32 (or coarse 10-24) bolts/screws in my Lycoming O-360.
 
Yes, the coarse threads can take more torque, but in this case it's simply a matter of following the manufacturer's requirements.

Torque required is related to thread, lock washers, friction (the oiled bit) and material the bolt is made from.

In this case, I can't remember any 10-32 (or coarse 10-24) bolts/screws in my Lycoming O-360.

Thanks Gil,
I now understand. My interest is solely in the airframe application, but this table led me to torque the AN3's to 49ip. I have replaced them all. I now refer to the table from Vans!!
Good day to you.
Johan
 
In this case, I can't remember any 10-32 (or coarse 10-24) bolts/screws in my Lycoming O-360.

I don't think I can come up with any 3/16" dia bolts/nuts on the O-320 either. Seems the smallest I've seen is 1/4-20.

It hopefully goes without saying that these torque values are NOT to be used with standard AN3-AN7 bolts (or their fine-thread NAS equivalents) on your RV airframe.
 
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