Hardness of Hooks

I did some googling out of curiosity, but I couldn't find any answers...so I measured it my damn self.

The BD Talon measured a hardness of approximately Rockwell C 34, which translates to a tensile strength of about 160,000 psi (depending on the chart you pick from the internet).

Interesting info, thanks!

Does psi translate into newtons or kilo newtons or some other measurement I might be more familiar with?

BBQ wrote:Does psi translate into newtons or kilo newtons or some other measurement I might be more familiar with?

Sure, 160 ksi translates to about 1.1 GPa.

BBQ wrote:Does psi translate into newtons or kilo newtons or some other measurement I might be more familiar with?

N/m^2 is an equivalent. If you are looking for how many KN it will take to break a hook, that is not what the OP is talking about.

apoet wrote: N/m^2 is an equivalent.

and 1 N/m^2 = 1 Pa, so 160 ksi = 1.1 GPa or 1.1 GN/m^2.

Be careful about translating hardness into strength. You can manipulate just the surface hardness without affecting the majority of the base metal. However 150 to 160 ksi is a very reasonable strength for steel.

Tensile strength (aka yield strength) is a material property. You can't translate into strength of a part without knowing the dimensions of the part and how its loaded.

You'd have to do a bunch of math for each hook and configuration to figure out what a kN on the rope would mean for a given tensile strength. Can't help you there; I'm just a software dork with access to a hardness tester that's more than twice my age.

I really just did the measurement because hooks are advertised as 4130, and I remember seeing somewhere that they're hardened.

NegativeK wrote:You'd have to do a bunch of math for each hook and configuration to figure out what a kN on the rope would mean for a given tensile strength. Can't help you there; I'm just a software dork with access to a hardness tester that's more than twice my age. I really just did the measurement because hooks are advertised as 4130, and I remember seeing somewhere that they're hardened.

Doubt you can calculate the strength of a hook and produce a useful number. Maybe to guide design but then after that it is going to be real world testing to see what the finished product can consistently do.

King Tut wrote: Doubt you can calculate the strength of a hook and produce a useful number. Maybe to guide design but then after that it is going to be real world testing to see what the finished product can consistently do.

Hmm, it´s not exactly rocket science. More like first or second year engineering stuff.

Jim Titt wrote: Hmm, it´s not exactly rocket science. More like first or second year engineering stuff.

I would bet that a simple FEA simulation would give relatively accurate results. I will try it out if someone gets me a CAD model of a hook they want to test along with its material properties.

apoet wrote: I would bet that a simple FEA simulation would give relatively accurate results. I will try it out if someone gets me a CAD model of a hook they want to test along with its material properties.

That sounds like pointless fun I can get behind. I'll follow up with hardness measurements of the BD Cliffhanger and Grappling Hook and a Leeper micro cam hook next week, but my CAD skills are best described as "hilariously shitty".

Every reference to material I've seen is 4130. If I'd half a mind, I would've gotten the folks with an X-ray fluorescence gun who passed through recently to zap the stuff I have.

Rockwell hardness has nothing to do with tensile strength.

Jim Titt wrote: Hmm, it´s not exactly rocket science. More like first or second year engineering stuff.

Ok, I am happy to be educated in this regard. Its the bend in the material (ie the pointy end) that I am wondering about. Obviously the hole for the sling would be simple I would think.

I certainly defer to the real engineers that know this stuff though. :)

King Tut wrote: Ok, I am happy to be educated in this regard. Its the bend in the material (ie the pointy end) that I am wondering about. Obviously the hole for the sling would be simple I would think. I certainly defer to the real engineers that know this stuff though. :)

With modern CAD/FEA software, this analysis is pretty trivial. That's not to say that actual testing to failure isn't relevant, but with simple geometry and loading the results should be reliable. I am not an expert in this area, but took a few related classes in college and have access to the software at work. If anyone has the means to test hooks to failure, I would love to see the results. I am sure BD has done extensive testing and simulation, but I doubt it is worth the investment for smaller companies to do FEA.

apoet wrote: With modern CAD/FEA software, this analysis is pretty trivial. That's not to say that actual testing to failure isn't relevant, but with simple geometry and loading the results should be reliable. I am not an expert in this area, but took a few related classes in college and have access to the software at work. If anyone has the means to test hooks to failure, I would love to see the results. I am sure BD has done extensive testing and simulation, but I doubt it is worth the investment for smaller companies to do FEA.

Pretty sure there´s a Talon in the "useless junk I bought once" box, no problem to put it on the tester over the weekend. Bat-hook holes in granite or in a steel block?

Jim Titt wrote: Pretty sure there´s a Talon in the "useless junk I bought once" box, no problem to put it on the tester over the weekend. Bat-hook holes in granite or in a steel block?

Steel block would probably be easier to simulate. Also, if you can get a picture of how you load it so I can accurately replicate it that would be helpful.

Now I need a CAD model of a Talon hook. Any takers?

I can also run the simulation, anyone has the alloy and temper treatment?
As for the CAD model... I could but I really don't have the time ;-)

Luc-514 wrote:I can also run the simulation, anyone has the alloy and temper treatment? As for the CAD model... I could but I really don't have the time ;-)

4130, Rockwell C 34 -- presumably through thickness, because they aren't that thick, right? I can slap together some (roughly presented) measurements when I do the rest of the hardness tests, to help whoever ends up being the cad.

All I've got for rockwell hardness -> tensile strength is stuff like link.springer.com/article/1… and conversion charts that indicate that seem to indicate that people are relying on the approximate correlation.

Jim Titt wrote: Pretty sure there´s a Talon in the "useless junk I bought once" box, no problem to put it on the tester over the weekend. Bat-hook holes in granite or in a steel block?

Bat-hook holes in granite, please.

Though I will need to review how to apply the load on the hook, probably lower third surface of the webbing hole.