Ed Fowler's Knife talk and ....

[pig]

Hi Ed and the whole knife family,
I did read Ed's "Knife Talk" very carefully. (I must prove it, of course to be believed, there is a printing error on the page 121. You should read 3/6 to be 3/16.) The book is invaluable to professionals but also funny to read to everybody most of all to revenuers. The article "The revenuers" is the best humorous essay I ever read.
I would have written directly to Ed, but he is probably buried in e-mails. (Ed kindly answerer to me earlier in this forum about "forger/grinded blades" and offered the book directly from him but did not answer my e-mail.)

Some thoughts to be shared (not only inspired by Ed's book):
(1)There are many different "schools" and books of knife making. It would be invaluable for a new beginner to get a comparative discussion about these matters. Some techniques presented differently in different books are matters of an opinion other techniques are simply presented in older books because new results are not known. (Well, I know that "everybody must find his own way", but still.)
-Triple quenching/ the grain structure gets worse with every heating (quenching)
-To quench "vertically/horizontally"
-Tempering the spine with torch or leave it unhardened partially
-.....................

(2) If we harden the tip and only oven temper it (350- 375 F) it will be brittle?

(3) "ABS spring smith test"- do not be offended I am joking!
ABS test practically reads- it spirit is: "Test the cutting and edge holding to be acceptable good. Test the toughness to the extreme limits". (Now I understand why Ed loves 5160- it is a spring steel!)
The test idea could be other way around: "Test the toughness to be acceptable good and test the cutting and edge holding to the extreme"

What kind of test? For example:
-Tip test: Hit the knife 1/5 inch (?) deep into a hickory block. Bend it suddenly sideways. The tip can't crack or bend and STAY BENT.
-Bending test: Bend the knife in a wise with a strong power (the power to be defined exactly). The knife can't crack or bend and STAY BENT.
-Cutting and edge holding: To be defined as extreme.

(4) Easy to sharpen argumen?
Two happy owners. Which one is more happy?
(A) "I sharpened my knife last week and must sharpen it to day again. No problem, it is easy to sharpen"
(B) "I sharpened my knife year ago and I must sharpen it to day again. No problem, I have a 'diamond stone'"

Also "easy to sharpen statement" comes as a consequence from the current ABS- test?
Any spring steel can't be extreme edge holding (low carbon for example).


Good blades: pig

 

[Emanuel]

Triple quenching/ the grain structure gets worse with every heating (quenching)

That's got my interest.
Does he happen to mention any more details about that?


Sorry, I know I should read the book.

 

[Cliff Stamp]

Pig, some comments on the testing :

Using a hickory block for the tip work is problematic as hickory, like any wood, is prone to changing over time due to losing or absorbing water, and there can be large varabilities from piece to piece. I dig holes in 2x4's to look at tip penetration and durability aspects of knives. In order to get a decent estimate of the relative performance of two blades, a lot of holes have to be dug in different pieces of wood to smooth out the variability.

You may want to consider a more standard material, or simply use vice jaws. The amount of force used the the prying and speed of application are also important as it the angle used in the levering. Similar for the bend test of the full blade, the angle of the bend and the force required are necessary indicators of performance. All knives will bend to some degree without breaking or taking a permanent set.

Cutting ability can be quantified by how much force is required to make a cut which can be determined in any number of ways. Different materials should be used to test the cutting ability at various heights. Knives compared on thread, 1/4" poly, 3/8" hemp and 1" hemp can all give different relative abilities due to one having a more acute edge but the other a thinner edge and main blade bevel.

Edge holding is influenced by wear resistance, strength, corrosion resistance, impact toughness and ductility. All of these aspects can cause the edge to blunt by either removing steel from the edge, or lowering the alignment. Cutting different materials can require various aspects more so than others so you will want to look at a variety of materials to get a complete perspective.

Ease of sharpening is determined by three main factors :

1) Resistance of the edge to damage. If the edge chips, dents rolls, rusts, or suffers excessive wear in use, a lot of material will have to be removed to sharpen - this will make sharpening very time consuming. Ideally a sharpening session should only require a minimal of metal to be removed as there was no significant damage and just microscopic wear or alignment issues.

2) Edge geometry. The more narrow the edge bevel, the faster it will sharpen due to a higher pressure on the hone for a given applied load and a directly lower amount of material which needs to be removed to make the edge bevels meet cleanly again.

3) Burr formation. The steel should be crisp enough to allow the edge to take the required level of finish with inducing the formation of a heavy burr of bent steel. This problem is minimized with grain refinement and higher hardness levels, with the counter aspect being that you can't go so hard as to induce ductility or toughness problems.

You might also want to consider testing the edge impact toughness and ductility. How heavy an impact can the edge take before chipping, and how much force does it take to bend it out of place and how much will it bend out of place before it rips / tears.

-Cliff

 

[pig]

To Emanuel's question:


Yes, triple quenching is presented in the book in the form of an article published in the Blade magazine. Ed has pretty convincing empirical data about that (diagrams also). Also he explains carefully the test organization. The test looks as scientifical and reliable. The test is done by many peoples involved.
The steel is 5160.

The term triple quenching is mentioned very often in this forum and I did not know about it's meaning earlier.


pig

 

[Emanuel]

Thanks pig, I'll have to look out for that.