Cutting Tests

Laredo7mm

Laredo7mm

Joined
Jul 8, 2002
Messages
1,240
Hey all, I want to do some testing on my blades. I want to be able to quantify the edge holding capabilities of my knives. I have read some stuff on the internet and found various methods. Here is what I have found:

1. 2 x 4 chopping
2. 2 x 4 slicing
3. Hanging Rope - How many strands can be cut with one swing
4. Non Hanging Rope - How many cuts can be made
5. Cutting thru quarters, paint cans, beer cans, etc
6. Cardboard Cutting - How many inches of cardboard can be cut

I understand that some of those tests not only test edge retention, but also edge geometry and blade shape/design.

I would think that the cardboard test would be best for testing edge retention.

Would that be correct?

If not, what would you recommend?

Also, what is a good baseline? For example; my knife cuts thru 100 linear inches of xxx weight cardboard before it needs to be sharpened. Is that good or bad?

Any other tests that you do, or know of?

Thanks for your help.
 
beluga-

I was planning on using that to qualify my blade as being dull. When the blade couldn't shave arm hair any more, the test would be done.

If I use that as my test to dull the knife, well, i think I would have to shave my arms, legs, chest, and back:eek: :eek: :eek:

That wouldn't be pretty.:D


Gouge-

How about cat neutering?:D Damn, I could have just saved some Vet bills.
 
For a quick test while sharpening I like to use a cheap horse hair paint brush. A knife that pops arm hairs might still not bite on horse hair. You can't really push the hair against anything (like skin) and they are slick so it really has to be sharp to bite. Plus, I don't walk around with bald spots. It's easy to test all spots on the edge.

When I have a blade that all parts of the edge will pop bristles without skidding, I'm set.

It isn't good for an edge retention test, nor is it a good cross-section test (like hanging rope), but a good sharpness test.

It would be interesting to use it in a cardboard test. You'd use a lot less cardboard, before it'd fail vs. hair shaving.

FWIW

Steve

PS I think you can group the tests like this:


Brittleness:

2x4 chopping
Brass Rod

Edge Retention

Cardboard Cutting
Rope Slicing
Rubber Hose Slicing

Cross Section/Sharpness

Hanging Rope

Sharpness

Arm hair shaving
Horse hair shaving
Gnat neutering
 
I n much of my testing as of late I have tried to get things as standardized as possible and remove the human factor whenever I can. Human hands can skew results, it is that simple.

Lets take popular rope cut. Not the hanging cut, but the repetitive bench top cut, the hanging cut is so technique oriented that I consider it almost useless in the determination of the knifes abilities. Somebody not practiced in cutting could have difficulty with even the best of knives, while an old pro could pop it with anything that has a bevel.

With the bench top cut there are some things to consider, one can cut through the rope dozens of times with a knife and not show much change in the edge at all, but then one can change their technique and completely dull the knife in one pass through the rope. If it is one thing that my testing has shown me, it is that many of the traditional tests say nothing more than “I think I like this knife better than that knife.”

I have gone to a reciprocating machine that I made, to saw through materials with the same stroke and the same 10 lb. pressure every time. I have found some amazing things about edges by using this method in combination with microscopic examination after a set number of “strokes”.

Rope is not the best medium to test things on, due to inconsistencies and the way it reacts to softer metals. Cardboard seems very good for a serious all around test of an edge.

For extreme sharpness I have adopted the cutting of cigarette paper to be a pretty good standard. I recent tests of many steels, most blades could no longer cut cigarette paper after 10 strokes across a rope. Even fewer could survive 10 strokes across cardboard. Under the microscope all the edges showed marked degradation and where considered “dulled” by the test standards, yet all would still pop hair cleanly off my arm. I have since dispensed with the hair-shaving test in all but primitive field-testing.

2x4’s are fun but they are some of the softest woods the knife could be exposed to in future use, I like to expose that edge to the extreme and then rest assured that its working life will be easier than what it has survived. . To be certain of the strength of the edge I will chop up white tail dear antlers and then closely inspect the edge. If I still have doubts I have even taken to smacking a ½” brass bar and then checking for deformation. If I have any doubt about the tips of my blades, I have found that a drop from 5.5 feet point first into a ½” steel plate will give me some reassurances (this is done on the bare blade before handle and fittings).

I realize that I have spent much more time and money than is probably necessary for the knifemaker that is not into in-depth research, but I believe that the best all around test, for those who just want to make knives, is heavy workouts in practical use. One of my favorites for larger blades is to ask a friend if the needs a fencerow cleared out and spend an afternoon whacking.

Handle designs are often overlooked also, so I like to keep old hardwood barn beams near my shop (8”x8” or so) and let loose on them for a while and then see how my hand feels after a few minutes.
 
My testing consist of fairly simple methods that give some idea of what I'm doing, not real scientific though.

I try to get as thin a convex edge as I think I can get away with. I first use the brass rod test to check my temper, them to the rope cutting, since it's not exactly consitant I do a couple of cutting runs, side by side with a stainless check blade for comparison. After that I re-sharpen and whittle and hew on some oak and hickory boards, then I've got an old dried cow shin bone that I chop some flakes off to check edge toughness. Also while grinding the edge on I do the Fowler methoud of sticking the point into mild steel, in this case the sheet metal base of my disk grinder.

If the edge is damaged I make it a little thicker and retest.

The cutting of coins and nuts and bolts and nails are a little out there, but I've done that on a couple just to see what they could take and to compare steels and heat treats.

As was said don't forget handle construction and ergonomics, edge holding is only part of a knife, how it feels in your hand and how secure and how much pressure you can apply is also very important. Also whether or not the handle will come apart under extream conditions.
 
Like Kevin, I have developed several standard tests to evaluate edge holding, sharpness and overall cutting ability. I save the 2X4 tests for testing swords for ultimate toughness as they are not really a consistent test media IMO. I usually have tatami omote mats here that I test knife blades on as I teach and train in Japanese sword arts and I find them to be a very consistent cutting media. They are semi abrasive and seem to dull an edge much like cardboard or paper...I get mine from Mugen Dachi co, http://www.tameshigiri.com/

A simple and available alternative for me is to roll up plain old 8 1/2" X 11" sheets of note book or computer paper into tubes about 1/2" or 1" in diameter and then stand them on the edge of a table (in a safe place of course) and cut them with clean downward slashes and chops. For larger Bowies or camp style knives you can roll 2 or 3 sheets into a single tube for a greater challenge. Paper like this is surprisingly consistent media and you can usually salvage a lot of it from any office as scrap. It is similar to the rope cutting tricks in that there is some technique involved what with edge alignment and blade angle. 35 to 45 degree cuts are the most effective. My point is that you will be surprised at how quickly the blade dulls in tests like this against ordinary paper and you can tell after 25 or 30 cuts how the edge is retaining it's sharpness. Also I find that slicing single sheets of notebook paper to be a very good and consistent indicator of how sharp the edge is...much better than shaving hair.

For larger and more robust blades I cut phone books. Again, these are available at certain times of the year and you can collect them from friends and family and get quite a few of them. They are not easy to cut, are abrasive to the edge, and very consistent media. The added bonus is that they are like chopping 2X4's in that they can *really* be hard targets.

All knives are different and I personally find that edge geometry and technique can sometimes affect the ability of a blade to stay sharp and effective even more than steel type or heat treat! It does not surprise to me that identical blades in different hands against different materials often disappoint the user. Even if you cut the same media with the same knife with different people the edge retention, whether real or perceived, will often vary considerably. I have seen sword students fail to cut with a particular sword consistently and give it up with a shrug saying "it's too dull" and then see another student pick up the same blade and cut the same target cleanly and consistently.

Standardizing tests for the purposes of blade evaluation is an art for knife makers in itself and worthy of much more discussion than it gets.

Brian
 
The testing of knives is a science, requiring skill, knowledge and a well thought out direction of purpose. Your testing will lead if it is well planned and carefully executed. A reference blade is a must for comparison. If you don't have the coordination or skill to acomplish a certain test, find a reliable substitute.
 
The oak lumber from old shipping pallets makes a good test medium. These are usually well seasoned, about 3/8" x 6". I feel that sticking to the same test medium is important. With experience you discern more. I had a blade recently I had ground very thin. Upon chopping through the pallet wood, I rolled the edge. I resharpended at a slightly more obtuse angle and corrected the problem. It is as much about observation as medium.
 
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