Cr-V vs Cr-Mo for impact accessories

[JHZR2]

Ive read plenty of discussions about the use, pros and cons of Cr-Mo for impact versus Cr-V. But what about extensions, U-joints and related stuff?

Granted, nobody wants a socket to blow up in their hand, which apparently can happen with the cheaper Cr-V stuff. But an extension should do just that - extend and minimize energy losses... So Id think you would want a hardder, more rigid item... Of course, the torque under impact, perhaps needs some give to be easier on the anvils or to prevent breakage... What do I know.

So, do you want extensions to be Cr-V or Cr-Mo? Ive seen that HF lower end impacts and all extensions are Cr-V, vs Cr-Mo. I tried seeing what snap-on used, to see the opposite end of the spectrum, but they don't seem to say.

So, whats best for impact?

 

[Rand]

cr-v is good for non impact, impact you generally get cr-mo

with impact I dont use any extensions to loosen and I have torque sticks for tightening.

It really depends on the impact wrench an aircat 1150 or other quality model.. even a HF earthquake you need better accessories than the 50$ HF electric model.

and of course there is different grades/qualities of both metals.

 

[JHZR2]

I get it that this is the case for sockets (the HF cheap sockets seem to me to be an anomaly, and are probably the rejects that get spray painted black and sold as impact sockets).

But extensions may be another story... thus the question.

Id rather never use an extension on an impact, but sometimes it is handy.

 

[artificialist]

With so many alloys for tool makers to choose from, why limit the selection to Cr-Mo and CR-V? Premium toolmakers don't always say what alloy they are using, could it be that they are using things like cobalt?

 

[JHZR2]

Originally Posted By: artificialist
With so many alloys for tool makers to choose from, why limit the selection to Cr-Mo and CR-V? Premium toolmakers don't always say what alloy they are using, could it be that they are using things like cobalt?


I don't have a play there. Ive just always seen Cr-V and Cr-Mo listed. If a vendor uses a proprietary, better alloy, Id think it would be listed and advertised...

 

[brages]

Stronger steels aren't really any stiffer, so it wouldn't matter from that standpoint.

 

[Kestas]

I agree with brages. Rigidity reflects a material property called "elastic modulus." Alloy may have a significant effect on tensile strength and ductility, but won't have a significant effect on rigidity.

 

[JAG]

Originally Posted By: Kestas
I agree with brages. Rigidity reflects a material property called "elastic modulus." Alloy may have a significant effect on tensile strength and ductility, but won't have a significant effect on rigidity.

+1

 

[JHZR2]

Originally Posted By: Kestas
I agree with brages. Rigidity reflects a material property called "elastic modulus." Alloy may have a significant effect on tensile strength and ductility, but won't have a significant effect on rigidity.

So what are we really going after with cr-mo vs venadium alloys? My understanding was more give of one sort or another. I see lots of terms like one being softer than another or one being tougher, which has no technical basis.

I have read that the mo alloys are more malleable, which effects their ability to absorb some of the impact and not shatter.

The thing I'm after is that the forces associated with an impact socket undergoing impacting and torquing on/off may be different than the design points of an extension. Shear, just like the coupling between an engine and generator or gearbox, and twist of that coupling prior to it shearing, seem to me to be the effects of interest, In something with repetitive pulsating beating with high torque, the last thing you want is for any torque to be lost in the twisting of the extending coupling.

 

[Kestas]

Higher yield and tensile strength, and toughness. It's hard to get both. But alloying with heat treatment can do it.