Mechanism for measuring force application

[sputnick]

I've finished moving into my new house (no more apartment living for me!) and I am no longer restricted to using the kitchen table as a work bench. As such it is time to come up with a standardized method to measure sharpness and cutting ability.

I would like your ideas on how best to measure force application in various modes.

My mettler 510g balance (.001g readability) is only suitable for lightweight jigs. My main concern in using thread is the required weight of the apparatus in order to obtain suitable and repeatable tension. What have you guys rigged up?

If using a method where the thread is applied to edge (whereas the method above would be applying the edge to the thread) the limit on maximum weight is placed on the knife and whatever holder is required to keep it upright on the pan. In this instance the weighted thread would be lowered onto the edge by hand.

Am I going about it all wrong? What approach has worked best for you?


Measuring cutting ability will be a bit trickier and will likely require a scale I don't currently own, any thoughts on that?

 

[Cliff Stamp]

There is some discussion of thread cutting here :

http://www.cutleryscience.com/articles/sharpness_review.html

In regards to cutting ability, find something that is binding but not very stiff, split small pieces of balsa for example or cut small sections of a medium density vegetable or thin section of styrofoam.

-Cliff

 

[Wayne G.]

Rubber bands are cheap and should be fairly uniform. I made a holder by cutting an opening in a piece of 2x4 so that a rubber band could be stretched over the outside giving it modest stretch. With the wood holding gizmo on a scale the knife edge is pushed down on the slightly stretched rubber band and the pressure to cut it measured. I see lots of variables with this but it is a start. I’ll get a picture of it and post it.

 

[gud4u]

Another idea I've been too lazy to impliment, would apply to slicing sharpness/dulling testing:
- Fixed-tension cord held taut with spring pressure.
- Blade edge fixed at a constant angle, such as 10 degrees above/below horizontal.
- A machining fixture with crank to draw the blade horizontally.
- A rule to measure distance traveled as the blade is drawn through the cord.

Then:
- Move the blade to contact with cord.
- Crank the blade horizontally until the cord parts.
- Observe distance traveled to cord-parting.
- Dulling/duller is measured as increased horizontal blade edge travel.

Such a rig would eliminate the need for a scale to measure applied force on the blade - eliminating that variable. Spring tension on cord would reduce wedging effect as blade bites into the cord.

Such a rig is probably to brute-force for thread-cutting, but might apply for materials such as rope or nylon or cotton clothesline cord - where the distance-to-parting would be more pronounced for the sturdier materials as dulling progresses.

As you might imagine, I have not attempted to patent this idea!