Bolt thread loading

[johnfin1]

I was looking at this chart and I dont understand why the numbers are different. Says the working load for a 1/4 unf bolt is 160 lbs (tensile) yet underneath on the lower chart is says 2700 for the same bolt.

http://dodgeram.org/tech/specs/bolts/SAE_bolt_strength.html

 

[rb1957]

T = Pd/5 ... the same torque on a smaller bolt will cause a higher tension

 

[johnfin1]

I thought course threads had a higher pull out in shear then fine threads but according to this fine threads are stronger. What is the truth?

http://www.tapmatic.com/tech_manual/drill_depth.html

 

[desertfox]

Hi johnfin

Yes finer threads are stronger

 

[desertfox]

Well actually depends on actual loading, finer threads have a slightly larger tensile area than coarse but coarse threads don't strip as easy as coarse.

http://www.bestbolt.com/white_papers/white_paper_08.pdf

desertfox

 

[desertfox]

sorry coarse don't strip as easy as fine threads

 

[johnfin1]

I am talking about stripping strength not bolt strength. Look at page 4. So what do you mean desertfox when you say threads are stronger?

http://www.fastenal.com/content/feds/pdf/Article - Screw Threads Design.pdf

 

[desertfox]

Hi johnfin1

That coarse threads are better from a stripping point of view than fine threads.

desertfox