Tensile and Shear Strength 3

[theMEintern]

This is probably a dumb question, but no one i work with seems to know the answer.

I am looking for a book/chart that has the tensile and shear strengths of several different Socket Head Cap Screws. I have been told to call a supplier, but i want to have a hard copy format to keep at the office for anyone that needs it. Does anyone know where i can find this?

 

[prohammy]

theMEintern,

Try this link (I can't view it myself, our web security blocks it on me, but it looks like the right sort of thing)

http://www.boltdepot.com/fastener-information/Materials-and-Grades/Bolt-Grade-Chart.aspx

it comes from

http://en.wikipedia.org/wiki/Screw

links at the bottom


Kevin

“Insanity in individuals is something rare, but in groups, parties, nations and epochs it is the rule” Nietzsche

 

[eromlignod]

If you need a rough figure (like if you're going to add a safety factor anyway), you can simply calculate the strengths based on the annealed material and a diameter equal to the minor diameter of the threads. This gives you a worst-case figure (neglecting notch-sensitivity, etc.).

Don
Kansas City

 

[metengr]

If you know the ultimate tensile strength of the material, you can estimate the shear strength using the equation below for carbon and low alloy steel;

shear strength = 0.6* UTS

 

[theMEintern]

Here is the situation.

I am designing a lifting fixture to pick up and object that weighs roughly 35,000 lbs. I need to know how many bolts to put into the object, as well as the fixture itself, so that I know that the Cap screws wont fail ad drop the 35,000 object to the floor. I am looking at using 1"-8 and 1.25"-7 cap screws. I just need to know how much 1 of each can old in tension and in shear so I can optimize my design.

 

[metengr]

Can you weld a lifting lug on the object instead of attempting to design a bolt-on lifting lug?

 

[civilperson]

Depending on the design of the lifting mechanism, any percentage may be applied at any lifting point. Thus, a four point harness may have 25%, 50% or 100% of the entire load acting on one lifting point, (depending on tipping and swing of spreader assembly).

 

[CoryPad]

The link prohammy gave you is a decent starting point. The actual values for mechanical properties are shown in consensus standards like ASTM A 354 Specification for Quenched and Tempered Alloy Steel Bolts, Studs, and Other Externally Threaded Fasteners and ASTM A 574 Specification for Alloy Steel Socket-Head Cap Screws.

Shear properties are listed because you aren't supposed to put threaded fasteners in shear. Of course they are placed in shear, so general equations like metengr's are used. Try to have a full body shank (not the threaded section) through the joint's shear plane.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[theMEintern]

It has to be bolt on so it can be easily removed.

 

[rb1957]

"... so I can optimize my design." ... nice idea but is it worth it ? safety, and a quick analysis, is more important (IMHO).

demonstrate that your structure can handle the loads ... worry about where the cg of the load could be, what SF do you need to lifting a load ? (i'd use at least 3) ... maybe consider one bolt in a group to be ineffective (ie need 5, use 6) ... worry about the shear/tension interaction (i'd use Rt^2+Rs^2 = 1, Rt, Rs = applied load/allowable; 'cause it's slightly conservative and much easier to use)

 

[theMEintern]

rd1957

You are right. I am after making sure I have enough bolts in the fixture so it does not fall. Onc I know that I will add more bolts so i know that the FOS is at least 3.

 

[GregLocock]

In an ideal world:

You do not use bolts carry loads in tension.

You do not use bolts as shear pins.

Bolts are designed to be used to draw the two parts together. The load is then reacted in shear between the two parts, by friction alone.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Kinsrow]

How about the use of bolts for gasket design? this bolt connection , ussually, is under tension in this case.

Kinsrow.

 

[40818]

RB1957 is correct, but if i may put my opion forward, i would have a factor of 8 for a lifting apparatus, cant remember where it came from, but its the number that is rattling around the back of my mind. I might be tempeted to use a different shear/tension interaction depedning upon the material of the bolts you decide upon though.

And though greglock is correct, but in the real world bolts are used to carry tension loads, especially in aircraft structures, thats why you can get a variety of bolts for shear or tension applications.

 

[KENAT]

I think 40818 may be correct, I seem to remember that number (8) too.

 

[Tmoose]

http://www.spstech.com/aero/prod_lit/socket_brochure.pdf

page 8 - double shear only (as it should be)

Last 2 years I did some work with a big defense contractor for a division of the US Navy. We ended up having to provide calculations proving between 3X and 5X factor of safety (for lifting), and slings etc rated for a 4 point lift failing to become a 2 point lift, even though the item being lifted would not physically handle being lifted at 2 points, and would have been hopelessly unstable (picture yo-yo) with most combination of 2 point lift.

FEA usually delights in pointing out that several of the bolts in my brackets, etc are completely superfluous. The solution is Thick flanges and keeping bolts as close as close to gussets (or is it gussets close to bolts?) as wrench clearance permits.

 

[mmart]

Mark's Handbook of Mechanical engineering. Chapter 8.2 machine elements