Building A Better Sharpness Tester

Vivi

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Here is a photo of my current sharpness testing device, similar to Nozh2002's.

It works pretty well. I'm getting fairly consistent results that give me a better standard than "It can shave arm hair" or some such. Right now I'm using some sewing thread, which was the thinnest thread I could find. Seems like its working well enough. I've been testing edge retention using corrugated cardboard cutting against the "grain" using pushcuts restricted to a marked portion on the blade. For instance, the Kershaw EnerG pictured measures between 30 and 35 grams sharpness when its freshly sharpened. After cutting 30 feet of cardboard, the sharpness measures 50g, after cutting 60 feet it measures 80g and so on.

This is my first sharpness measuring device so I'm looking for ways to improve it. I definately want a quicker, more secure way to attatch the thread than wrapping it around those two nails. I could stand to widen the notch a little, especially for testing large knives. For thread I'd like something that's widely available and has a consistent quality to it for better results that others can also easily duplicate. I don't know what standards sewing threads adhere to, if any. I do very little sewing in my liesure time. :)
 

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I made a similar sharpness tester except I used a 2 1/4" hole saw to cut the edge out of the block of wood. I'm thinking of replacing the nails with a couple of screw type speaker terminals to speed up thread replacement.
 
I use, where you have the nails, two screws with a fixed nut and a wingnut between which I squeeze the thread.

I am still using this:
 
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