VIDEO: Why polish and reprofile? -- answered

I did find it interesting. Would like to see it again only with a push or pull stroke instead of just straight down pressure.
 
Badhammer said:
I did find it interesting. Would like to see it again only with a push or pull stroke instead of just straight down pressure.
Click to expand...

Thanks to all for the positive comments. I really enjoy doing these things.

Badhammer, That would be interesting, but I think it adds a variable (the amount of push or pull perpendicular to the direction of cut) that is nearly impossible to isolate (with this ghetto-rig anyway). I may try something in the future though.

I think you are getting at a very good and important question though...regarding how we use knives and how this "test" is a limited window into one type of cut. I hope everyone realizes that this test is VERY limited by design. Without limitations, reproducibility suffers drastically.

For those interested...I repeated these cuts multiple times and the numerical results were reproduced exactly (within the precision of the toys I was playing with). While not incredibly scientific, it demonstrates that the method has some merit.

I did not want to focus on the numbers too much beyond demonstrating that the differences were large enough to see and feel.

Thanks again!
 
Nice test:thumbup:.

You would almost say a good slicer can't get any better but you proved it with these cutting tests.
 
Thanks for the excellent test. I couldn't quite catch the pressure at the breaking point, but it looked like most of the advantage was picked up by reprofiling and polishing to 15 degrees. The 10-degree edge was only slightly better. Is that right?

Were you able to measure the angle of the stock blade?

We you able to control the tension on the string somehow?
 
very cool video. I like practical videos like this that clearly show results and are easy to follow. Nice job
 
Twindog said:
Thanks for the excellent test. I couldn't quite catch the pressure at the breaking point, but it looked like most of the advantage was picked up by reprofiling and polishing to 15 degrees. The 10-degree edge was only slightly better. Is that right?

Were you able to measure the angle of the stock blade?

We you able to control the tension on the string somehow?
Click to expand...

The tension in the string was achieved by feel only...they were all "about" the same. Running the "test" 3 (plus) times on each blade profile (and getting the same numbers) demonstrated to me that the variability in the string tension was not significant relative to the ability to measure cutting force.

I also ran several other stock Spyderco blades to better understand the variability. I only have 4 Spyderco factor edges at my disposal that have not yet been used to cut anything. Scores on this test ranged from 3.6 pounds to 5.0 pounds. If I handed any of them to an average user they would run whatever test available to them (thumb, shaving arm hair, etc.) and likely conclude that all were DANG sharp. I would like to stress that Spyderco does a fantastic job of delivering sharp knives IMO.

I made no effort to measure the factory edges. They all appear to be about 30 degrees inclusive with a micro bevel.

In the video the results were 4.2 pounds on the stock blade, 2.6 pounds on the polished 30 degree inclusive blade, and 2.0 pounds on the polished 20 degree inclusive blade. Please do not fixate on the numbers as they are somewhat arbitrary and different types and thicknesses of string will change them, but I think the relative differences are the real point.

You are correct the big advantage is gained between the factory edge and the 30 degree polished edge in this example...but if you have a particularly good factory edge that cuts like (or better than) the best one I have (3.6 pounds) the differences are slighter.

Additionally, the difference between 2.0 pounds and 2.6 pounds "feels" significant (to me)...but as I say in the video, there is a price to pay in durability for thinning the edge!

I am doing some other "testing" also, I will probably be sharing those results in the future.

Thanks again to all for the positive comments and thoughts!
 
Thanks again guys. I am happy to have like minded people to share with. I have learned more than I have shared. I owe you guys for that!
 
Very nice test and quite a display as to how simple it can be to build a rig to test various edges.

One thing: As the video started and I realized how the test would work (mechanically), I though "Why metal at the bottom of the cut? Why not fit a small piece of pine or redwood or something in case the blade hits the metal?" Sure enough.....click!

Anyway, just a thought. I like the idea and the demonstration of regrinding the secondary bevel. I regrind most of mine to about 12 degrees. Not because I have scientifically tested it like you did to determine its value, but rather, because it just made sense that a thinner, more acute angled edge would slice better. It was nice to see your test prove it scientifically.

Thanks for the video!
 
That was a great video. Many don't seem to realize how well thought out this type of test is (not talking about people in this thread). Excellent presentation:thumbup:
 
I found the test to be very informative. I think it illlustrated what edge I'd want to put on the knife I've chosen for particular tasks. i.e. hard use, food prep, general duty.... good job :thumbup:
 
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