Edge Retention/Rolling Test Stand

[KnifeGrinders]

First effort with the new impactor design. Well it works. It works a little too well but that will be easily adjusted. Same knife but different edge location. Initial sharpness was 150. Here's the test setup at the conclusion of the rolling exercise.



The new impactor piston assembly weighs 250 grams and the additional weight in the cup is 1750 grams for a total of 2000 grams (4.4 lbs). If you recall, in our earlier test with the 5/16" rod end this amount of weight didn't affect the edge. With only the radius of the 1" diameter rod contacting the edge now, it did and substantially so.



The good news is that when you roll them this severely you can see the damage at 140X. We think that you should be able to identify the section of rolled edge. You can also see that we missed the impact point when we placed the impactor on the edge. The picture here is representative of about 1/16" of blade so we missed by about half that distance or 1/32". We need to get better at placement. Once located, there was no difficulty in taking fairly repeatable measurements in consideration of the damaged edge. 694 - 732 -712. We very much suspected that this was too much of a good thing and we were proven correct. We could only correct the edge by leather stropping back to around 325. We think that this failure (to fully correct the roll) must be caused by one, or in combination with, two things; either we have damaged (crushed) the edge apex or the roll is so deep that a piece of leather can't straighten it. As we said earlier in this thread, our experience tells us that a differential of around 300 is about the limit. If you're interested, the measurement adjacent to either side of the impact point was 148 and 153. 

Next stop...1000 grams.

Congratulations!