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AbelGus (Industrial) (OP)
16 Sep 05 10:07
I am looking for tables or formulas for pull out strength of bolts or studs threaded into aluminum.  In particular, I am threading an M12 X 1.75 forged stainless steel (alloy 316) eyebolt into 6061-T6511 aluminum or 7075-T651.  The thread depth is 20.5mm.
The eyebolt in question is a shoulder eyebolt with a working load of 3.4 kN.  I am concerned about straight pull only.  I want to ensure that the thread bearing capacity matches the permissible working load when threaded into aluminum.

Abelgus
Helpful Member!  rb1957 (Aerospace)
16 Sep 05 10:38
From AR-MMPDS-01 (you'd be able to find the same info. in MIL-HDBK-5) table 8.1.5(b1), a 1/2" diameter thread in 55 ksi (ftu) has a strength of 8310 lbs.  6061T6 has an Ftu of about 40ksi (that sucks), as allow a stregth of 4155 lbs (1/2 the 55 ksi value) = 18kN ... quite a bit more than your requirement
boo1 (Mechanical)
16 Sep 05 10:58
Consider using a threaded insert.  This will help you match the strength and reduce the galvanic potential.
IFRs (Petroleum)
16 Sep 05 20:05
Can't go through the aluminum, I guess.  Is this temporary, permenant, holding up something that people will be under, subject to getting wet, have vibration loading, carrying other loads?
AbelGus (Industrial) (OP)
16 Sep 05 21:31
These are M12 eyebolts with shoulder threaded into each end of a 1" x 3" x 48" long aluminum bar which supports woven wire fabric under an arcade.  There are three splayed cables the attach to each eye.  Static calculations have been performed (900 pages worth)for a 30 psf. windload that show the maximum load on any one iontermediate cable in the system is 178 lbs. (The end cables are more highly loaded and use different connectors and bars).  There is never a case where all three cable carry the 178 lb. load but assumining they did the outside max.load on the eyebolt would be 534 lbs axial to the bolt.  The bolt part of the eyebolt is 20.5mm long, m12 X 1.75.  The aluminum is post anodized after machining.  This is in a dry location.
AbelGus (Industrial) (OP)
16 Sep 05 21:34
Aerospace,

Is threr a way to access this table via the internet?
AbelGus (Industrial) (OP)
16 Sep 05 23:05
RB1957 (aerospace)

Is there any way to access this table via the internet.

Thanks

ABELGUS
Lutfi (Structural)
18 Sep 05 13:33
Listen to boo1. He is so right. I would use KEENSERTS or any similar product. There are many advantages to using them. to add to the advantages than boo1 listed, I would point out that you can replace the inserts and keep the parent aluminum metal threads undamaged.

Here is a link to KEENSERTS links to web sites:

1.    Advantages of using the inserts:
http://www.barnhillbolt.com/pdf/keensert.pdf#search='keenserts%20by%20tridair'

2. KEENSERTS web site
    http://www.keensert.com/

Good luck

Regards,
Lutfi

AbelGus (Industrial) (OP)
18 Sep 05 20:56
Lutfi & boo1

The threaded inserts are a good idea for a number of reasons.  The step up in diameter increases strength (tho I am OK there).  The other good thing is that the insert can be backed in and out slightly to allow the shoulder eyebolt to be in the correct orientation - this is easier than trying to start the tap in the exact orientation, or shaving material of the end of the bar until the eyebolt sits right.  After it is correctly positioned the bar will be cross drilled for set screws.

The dissimilar metals is not really that mush of an issue between aluminum and stainless steel - particularly when Loctite is being used.  Also the anodizing helps.

Thanks
MikeHalloran (Mechanical)
18 Sep 05 21:58
The load I'd be concerned about is that developed when the eyebolt shoulder bottoms out and the assembly gorilla sticks a cheater bar through the eye and hangs from it, just to make sure it's 'tight enough'.  

By eyeball, the thread engagement seems a little short for that loading condition.



Mike Halloran
Pembroke Pines, FL, USA

rb1957 (Aerospace)
19 Sep 05 10:17
5J is out of date, but the data is still good ...
http://www.reliasoft.org/mil_std/mil_hdbk_5j.pdf

check the transverse loads on the lug; the loads don't look like trouble, but it's nice to see a calc (to show things that were considered).

good luck

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