briand

briand

Well Known Member
I've been waiting to tighten the million screws that attach my tanks until I got a torque screw driver so today I ordered one and can't seem to find these torque limits anywhere.

My Standard Aircraft Handbook (where I expected to find them) only lists down to an 8-32 bolt (12-15 in-lbs.) which is prabably the same as a #8 screw but I'm not positive.
 
depends on material

Depends on the material the #8 screw is made from....

Which part number are you using?

gil in Tucson
 
AN509

For the AN509-8, which are made from 125,000 psi steel, my Airframe Mechanics book shows 12 to 15 inch-lbs. - they are treated like the bolts you mention in your previous post.

I don't have a #6 torque reference, but the AN507 screws are made from only 55,000 psi steel, and would be much less.
If they were AN507 at #8 size, I would expect about 5 to 7 inch-lbs. based on the material. The AN507 are not really considered structural...

gil in Tucson
 
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12-15

wow thats a little bit..tighten them down till they clamp then give em a bump.
 
ooops

briand said:
Don't tell me that. I just spent $50 on a torque screwdriver.
Click to expand...
ok i take it back..and dont forget to add drag torque to the 12-15 or you may never even get it started
 
#6 torque

I went and talked to our Mechanical designers at work and they pointed me to this table... small portion copied here....

Screw Size .138-32 (#6)

Lubricated Screw Threads 12 in-lb.

Dry Non-Locking Threads 14 in-lb.

Dry Locking Threads 16 in-lb.

Screw Tensile Stress Area (sq. in) 0.00909

This is for 80,000 psi material... scale it down for the AN507 55,000 psi screws, or use better screws... ;)
Also note that these numbers include an allowanace for the friction drag, don't add extra.... :) I guess they don't want the assembly people doing mathematical calculations.

These numbers are good for unmanned, guided, high speed aerospace vehicles.... should be good enough for our RVs.... :)

Test first....

Data is derived from M. F. Spotts, Design of Machine Elements and Mechanical Engineering Design by Joseph Shigley.

gil in Tucson
 
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