Knife edge thickness/surface area

  • Thread starter Thread starter droc22
  • Start date Start date
  • Tags Tags
    Area Edge Knife
Click For Summary

Discussion Overview

The discussion revolves around the thickness of knife edges and their implications for cutting force, specifically in the context of slicing an apple. Participants explore the relationship between blade thickness, contact area, and the force required to cut through materials, while also considering the effects of shear forces and friction.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant calculates the force needed to slice an apple based on skin bursting strength and blade thickness, arriving at a force of 1.1 N, but seeks confirmation or documentation on knife edge specifications.
  • Another participant questions the appropriateness of using skin bursting strength, suggesting that cutting involves shear forces rather than just normal stresses, and offers to look for information on surgical scalpels.
  • A third participant recalls a previous discussion about the sharpness of knives, noting that obsidian blades can achieve a thickness of one molecule, while high-quality steel blades are significantly thicker.
  • One participant points out that the assumptions made in the initial calculation may not account for the round shape of an apple and the changing point of contact as the blade slices through, suggesting that friction should also be considered.
  • Another participant shares their own experience with knife edge thickness, mentioning a specific blade type and its dimensions, and expresses interest in understanding the strain it can exert on a material without causing damage.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the appropriate methods for calculating cutting force or the relevance of the parameters discussed. Multiple competing views and uncertainties remain regarding the effects of blade thickness, cutting mechanics, and material interactions.

Contextual Notes

Limitations include assumptions about the shape of the apple, the nature of the cutting motion, and the lack of specific references for knife edge specifications or cutting force calculations.

Who May Find This Useful

This discussion may be of interest to those studying material science, mechanical engineering, or culinary arts, particularly in relation to cutting tools and their effectiveness.

droc22
Messages
10
Reaction score
0
I'm having a hard time finding some documentation on the thickness of a knife edge. I need to calculate the force to slice an apple. I found the skin bursting strength to be 1.1 MPa. That means that assuming the thickness blade to be 10.0 micro-meters and the max length of contact with the blade and apple is about 10 cm, the force I get is 1.1 N.

Does that sound about right. I would rather not assume, if someone knows of a source of knife edge specification.

Thanks.
 
Engineering news on Phys.org
I don't know of a reference, but you may want to look at that strength number for skin. That may not take into account the shear forces that are present in a cutting motion. The failure of skin due to a knife would not be failure due to normal stresses. That would be like tearing the skin apart.

I'll look to see if I can find anything for surgical scalpels.
 
We had a thread about the sharpest knife in the world last year, but I can't remember what forum it was in. Obsidian blades can get down to a thickness of one molecule. I seem to recall that the best steel ones were somewhere around 50 times thicker.
 
are you just trying to find an approximate, becasue so far with your assumptions, you're working with a square apple and a straight blade and finding the force required to split the skin. With a round apple your point of contact intially will be very small and then enlarge as you slice through.

to cut a slice you'll probably have to take friction of the knife passing through the apple into account.
 
I am also having trouble finding any documentation on minimum edge thickness except my knife is CPM-S90V with a thickness of .150" and an included angle of 40 degrees. I just want to see how much strain I can put on a block of delrin with my blade without destroying it for 10 cycles or so.
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 8 ·
Replies
8
Views
6K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 46 ·
2
Replies
46
Views
7K
  • · Replies 16 ·
Replies
16
Views
3K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 17 ·
Replies
17
Views
5K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 5 ·
Replies
5
Views
11K