Allowable loads on small diameter fasteners

[DB1521]

AISC provides tabulated allowable shear and tensile stresses for ASTM A307, A325, and A490 structural bolts. When dealing with small fasteners such as SAE J429 Gr 2, 1/4-20 screws, where can one find specifications for allowable shear and tensile stresses similar to what is found in AISC? For example, Fv = 0.4Fy and Ft = 0.6Fy.

Also, this fastener is under large tensile load due to the torque recommended by the manufacturer. If I check the tension in the fastener due to the preload, it seems excessive. Is there a different specification for maximum tension on a preloaded fastener such as 0.9Fy? This joint requires a clamping force (hence the torque), and it experiences combined shear and tension loads (seismic).

If helping, please reference a legitimate source for fact checking if available. Thanks for any assistance.

 

[desertfox]

hi DB1521

Have a look at this reference:-

http://www.boltcouncil.org/files/2ndEditionGuide.pdf

also this site:-

http://www.roymech.co.uk/Useful_Tables/Screws/index_screws.htm

desertfox

 

[boo1]

consider reviewing

http://www.engineersedge.com/fastener_thread_menu.shtml

 

[MintJulep]

When dealing with small fasteners such as SAE J429 Gr ...where can one find specifications

Is this a trick question?

http://standards.sae.org/j429_199901

 

[Ron]

Many manufacturers provide mechanical data on their product. Otherwise, buy the standard as MJ suggests. Don't use coarse thread data for fine thread fasteners.

 

[DB1521]

All - Thanks for your help.

I'm not sure if the SAE spec or manufacturer data will answer this question. The question is, how does one calculate the allowable stress on the cross section of a bolt (those not covered by AISC)? I see that Fy and Ft is specified for the different types of fasteners. I'm assuming that normal practice is to use Ft as your maximum applied tensile stress. But what about shear? Do you use a percentage of the yield such as 0.4Fy? And who is the design authority that determines the methodology used for calculating shear and tension allowables?

I will check out the links and resources that have been recommended. Thanks!

 

[CoryPad]

Are you using AISC 360-05Specification for Structural Steel Buildings? Table J3.2? The only thing similar to this document that I have seen is Eurocode 3 Design of Steel Structures. The Research Council for Structural Connections (RCSC) has two excellent publications on this subject, Specification for Structural Joints Using ASTM A325 or A490 Bolts and Guide to Design Criteria for Bolted and Riveted Joints (which desertfox linked to above). Both of these are available at no charge here:

http://www.boltcouncil.org/Publications.html

Methods for analyzing pretensioned joints are included in VDI 2230 Systematic Calculation of High Duty Bolted Joints. A value of 90 % of the screw tensile yield stress is common. This is available for purchase at Beuth:

http://www.beuth.de

 

[unclesyd]

Here is set of tables from Engineered Parts that gives you quite a bit of information on different grades ofsmall diameter fasteners. Look under torque and tension and under materials. Along with the physical properties there is considerable information on other parameters.
You must not forget that this for properly marked fasters not for most big big items.

http://www.engineeredpartsinc.com/