Poor man's sharpness tester

theonew

theonew

Joined
May 16, 2006
Messages
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Check out this Link

This seems pretty easy and inexpensive to build and use. I'd just like to come up with a way to avoid having to eyeball the result.
 
That is a very nice idea. Got to try that. Should be a very quick test as well. Also proves the assumption in Nozh's thread that edge angle is of no (or no significant) consequence.
 
The angle changes cutting ability among other things, but not sharpness. It can be difficult to measure edge retention by only measuring sharpness when there are two knives with different edge angles because the one with a more acute edge will cut better even with the same sharpness.
 
I like it especially since it should limit any effect of tension regarding the testing medium and should therefore only require a single cut to get an accurate result.
 
Larrin said:
The angle changes cutting ability among other things, but not sharpness. It can be difficult to measure edge retention by only measuring sharpness when there are two knives with different edge angles because the one with a more acute edge will cut better even with the same sharpness.
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That's why I'm thinking about the Spyderco Mules :D
 
Larrin said:
The angle changes cutting ability among other things, but not sharpness.
Click to expand...

Well, there were some people that expressed doubts about that in the other thread so it is nice to see confirmation. Actually, it was also the opinion was expressed that thickness should influence thread (or rubber band cutting).
 
That is a clever idea. My only concerns would be a) consistency of the rubber bands as a test medium, and b) how granular the test would be over different ranges of blade sharpness.

Concerning a) consistency, I'd definitely want bands made of surgical rubber, no color or other impurities added, since not only should they be more consistent but they'll stay fresh (retain elasticity) longer.

As for b) granularity of the test ... well, I guess somebody's just going to have to give it a try! :)
 
Rubber band consistency definitely crossed my mind as well. I did some googling and didn't come across any suppliers of surgical rubber bands. Dog of War, any ideas? Thanks.
 
theonew said:
Rubber band consistency definitely crossed my mind as well. I did some googling and didn't come across any suppliers of surgical rubber bands. Dog of War, any ideas? Thanks.
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I googled "rubber bands" and "surgical rubber" and came up with a fair number of hits. These guys: http://www.dykemarubberband.com/ make kind of a thing on their website about quality, stating that their bands are 90% rubber, so seems like this might be an important consideration to other serious rubber band users. :) Another company that might be helpful: http://www.aerorubber.com/index.html. Plenty of hits from eBay for surgical rubber rubber bands too, I notice.

Another thought ... been some time since I've had home delivery of a newspaper, but I remember they used to come bound with nice, light, semi-translucent-brown rubber bands that looked to me a lot like surgical rubber. So the neighborhood paper boy might be a good source, probably cheap and as fresh as you'd find anywhere.

Think I'm going to have to give this a try myself, sounds like a fun project.
 
hmm, what about cutting them on a scale, stretched across a fixed jig, tension should stay consistent. That's a concern in the thread cutting.
 
But the nice thing is that you don't need the scale anymore, the rubber tension is a build in scale. All you need is a ruler. Probably even more accurately to read of as well.

Variance in the rubber band doesn't really worry me. You see the variance in the data set in the original link.
 
HoB said:
But the nice thing is that you don't need the scale anymore, the rubber tension is a build in scale. All you need is a ruler. Probably even more accurately to read of as well.

Variance in the rubber band doesn't really worry me. You see the variance in the data set in the original link.
Click to expand...

Plus it would be easy to calibrate a scale that relates the stretch in the rubber band into force applied.
 
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