Non-bolt fastener torques

[Flying Scotsman]

I'm a ways away from needing to know this, really, but I'm curious. Torque specs for bolts are commonly found (any standard handbook or the net), but what about other types of fasteners - namely, screws? CDI and other companies sell torque screwdrivers...and I like tools . But I can't find any torque values for AN screws (and there must be some, right?).

Also, what about flared-tube fittings and the associated nuts? Is there a torque value for those? I recall Van's put one on one of their SB's related to the fuel pick-up safety wire...but is there a set of torque values for the different sizes of fittings?

I did some searching but all I can come up with is the values for AN bolts and nuts.

 

[DGlaeser]

The reason is . . .

Torque on a bolt is to provide preload, which reduces fatigue due to loading & unloading of the joint in tension. Screws should never be used where that type of loading is important, so once they are snug, you are good to go - any added torque provides no real structural value.
If you're like me, the first time I ever torqued ana AN3 bolt to spec I realized that what I considered 'snug' for that bolt was actually over torque An AN3 bolt is the same dia. as a #10 screw, so if there were a torque spec for a #8 or #6 screw it would be even lower.
I use the clutch feature on my cordless drill and screwdriver, at a fairly low level, to prevent stripping out the head during installation, which also helps prevent stripping the head during removal.

 

[fl-mike]

Table 9-2 in AC 43.13 gives the torque values for tube fittings.
http://www2.tech.purdue.edu/at/courses/at308/Technical_Links/Ac43-13-1B/CH9_2.pdf

I use the table 7-1 values for screws. In fact, I usually use a socket on a torque screwdriver to tighten AN3 size nuts whenever possible.

 

[WilburD2]

AC 43.13

... is available at your friendly neighborhood FAA website. But for quick reference here is the aforementioned table 7-1 for torque values!

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/99c827db9baac81b86256b4500596c4e/$FILE/Chapter%2007.pdf

Good luck!

 

[Flying Scotsman]

Doh! I have a copy of AC43-13. Shoulda looked there, don't know why I didn't think of that. Thanks!

 

[Flying Scotsman]

If you're like me, the first time I ever torqued ana AN3 bolt to spec I realized that what I considered 'snug' for that bolt was actually over torque

Yeah, I was quite surprised at how little torque they take. Who knows how many (non-aircraft, fortunately) bolts I way overtorqued in my lifetime before I got a good torque wrench and started paying attention.