Arc-Lock testing

[Cliff Stamp]

I have seen the Arc-Lock described as :

<font face="Verdana, Arial" size="2">testing at over 1000 lbs force measured at the lock</font>

http://www.hascoind.com/SOG/nightvision.htm

Now while this sounds impressive as 1000 lbs of force is a lot, without knowing where and how this force was applied it is pretty much meaningless.

How far from the piviot was the force applied? Was the blade clamped to prevent spread? Was the force slowly increased or was it a sudden impact?

If it held at 1000 lbs at what point did it break? How many times can 1000 lbs of force be applied before the lock is functionally effected?

Was there any testing done on how the lock handles side torques?

-Cliff

 

[Ron Andersen]

Hi Cliff,

Thanks for your question. I know it is one shared by others.

You wrote:

<font face="Verdana, Arial" size="2">...while this sounds impressive...</font>

I hope you understand that other companies advertise with hyperbole while we try very hard to advertise realistically to our customers and non-confrontationally toward our competitors. Though the site you reference is not a SOG site, it does represent, in summary, the facts.

Cliff, as most SOG forum readers know, I am neither a metallurgist nor an engineer; I'm just a really nice guy and customer service professional, who happens to love knives. Any of the more techie information I pass along is relayed, and often not personally understood. This disclaimer aside...

I would like to first point you to SOG's BladeForums post introducing the Arc-Lock that was written by the lock designer (and SOG owner), Spencer Frazer.

http://www.bladeforums.com/ubb/Forum55/HTML/000066.html

To now answer some specific questions you brought up in supplement to the post linked above:

• Force was applied slowly until the lock pin failed by jamming, not severing, at 338 pounds of pressure 1/2" back from the tip, equaling about 1,183 pounds of pressure directly to the lock pin (this was on the Vision, with a 3.75" blade). The test was stopped when the jam occurred; no further pressure was applied to find out the total pounds of pressure required to completely close the blade past the pin. In other words, the independent test described the initial (and only tested) failure as resulting in a jam, not a closure of the blade.
• From my understanding, a hole was drilled in the blade 1/2" back from the tip and the lanyard hole was used on the butt end of the knife for the test.
• No direct "side torque" testing was done because the liners firmly hold the lock together and in place, and any side pressure/torque failures would happen only in circumstances not consistent with intended uses of a folding knife.

I hope this information has helped you out. If you have further questions, I'll see what I can do to acquire and accommodate technical answers for you.


------------------
Ron Andersen
Consumer Services Manager
SOG Specialty Knives, Inc.

Website: www.sogknives.com
Email: ron@sogknives.com


[This message has been edited by Ron@SOG (edited 04-04-2001).]

 

[Cliff Stamp]

Ron

<font face="Verdana, Arial" size="2">338 pounds of pressure 1/2" back from the tip, equaling about 1,183 pounds of pressure directly to the lock pin (this was on the Vision, with a 3.75" blade)</font>

Just a note on the language used, 338 pounds is a force not a pressure. 338 pounds of force at a distance of 3.5" from the pivot gives 1183 in.lbs of torque, a very decent amount.

If the 338 is actually a pressure, most likely in psi, then the force is significantly lower (considering the area of the blade spine) and thus the torque as well. However I don't think this is the case.


-Cliff