Breaking an Allen Wrench

[taylorbrown96]

Hello, I was wondering if anyone here knew of (or could come up with) an equation relating the tensile strength and the maximum force that could be applied to an allen wrench? Any help is appreciated.

 

[OldEngr63]

What direction do you want to load the wrench? A picture of your intended test/application set up would help make your question more clear.

In general, I think you will find that the wrench will bend/yield long before it breaks. Does that count as a failure, or are you only concerned with breaking into two parts?

 

[Bystander]

bend/yield long before it breaks

"Bargain bin" hex keys will; honest "Allen" brand? Depends on how much "shock" loading they've endured from impact drivers.

 

[felmon38]

Hi Taylor..., at first sight the bending stress at the base of the arm would be the more dangerous being the tension:
σ=F.l.y/I
http://en.m.wikipedia.org/wiki/Bending

 

[Ranger Mike]

i broke a lot of them over the years. when working on rusted old automobiles, pretty common. they snap before they ever take a bend and retain the bend usually.

 

[felmon38]

Ranger, I think this is fundamental your experience. Where was usually the position of the fracture ?

 

[Averagesupernova]

I have seen them all. Bends, breaks, twists, etc. On set screws the screw usually splits before the wrench is damaged.

 

[Ranger Mike]

usually the small ones break...and the fracture is close to the L , i have twisted a 1/2" (13mm) allen wrench..used a pipe to try to break loose an allen plug

 

[Dennis C]

I have always found the smaller fractional < 3/8" will strip the fastener before breaking a wrench.
When using the larger internal socket hex wrenches, it will sometimes need a "cheater / persuader / logic modifier" to loosen the fastener and that is what will break the wrench, but after using them for 30 yrs, I haven't broken many at all.