The Sharpmaker - Some Tests

[JDEE]

I’ve been using a Sharpmaker for some time now and have been developing a theory re the use of the fine versus coarse rods. This theory is really an extension of the “polished” Vs “aggressive” edge. Firstly, I noticed that with Spyderco Knives out of the box that in general they only needed a few strokes on the fine rods to clean them up and bring them back to “hair-popping” sharp. I firmed in the view that I was using the fine rods much in the same way that a butcher would use a steel although nowhere near as often. Thinking further on it I am of the view that by using the fine rods extensively (say 20 strokes per side) that I was in fact developing a polished edge on my blades – something that I don’t normally do preferring an aggressive edge on the most of my blades.

So I decided to develop a test to check out my theories – not having the cash to buy 2 Spyderco’s for the purposed I bought 2 Kabar Dozier Precision Hunters KA4062 Drop Points in AUS-8 at 56-58HRC folders which I nominated as “A” and “B”. Out of the box I took a piece of 3/8” manila rope and started cutting. Knife A made 10 cuts before beginning to slip and Knife B made 9. I then gave each knife 5 strokes per side on the fine rods. Back to the rope and both knives this time made 10 cuts before beginning to slip.

I then took Knife A and gave it 20 strokes per side on the fine rods NB all sharpening was done at 30 degrees and gave Knife B 20 strokes per side on the coarse rods. When I performed the rope test this time Knife A made 14 cuts before slipping and Knife B made 21 strokes. It looked like my theory maybe panning out so I went back to the Sharpmaker and repeated the 20 strokes per side. The rope test this times showed Knife A making 15 cuts and knife B making 28 cuts (nearly double). Now to check out the theory that the fine rods would work similar to a butchers steel – I gave both knives 10 strokes per side on the fine rod and went back to the testing bench. Knife A made 14 cuts and Knife B made 26 cuts. Back to the Sharpmaker with 20 strokes each side and repeated the rope cutting tests. Knife A made 15 cuts and Knife B made 27.

To finish the test I took Knife A and gave it 20 strokes per side on the coarse rods and it then made 26 cuts of the rope. So what do my tests show. In my view it provides us with the following:

A. It proves the assertion that an aggressive edge will out cut a polished edge in rope cutting tests; and
B. You can use the fine rods in much the same way as a steel.

Now like any tests you can always shoot a number of holes in it and I would appreciate any input from forumites on where I may have gone wrong or drawn the wrong conclusions.

Given my views that you could use the fine rods as a steel maybe Spyderco may like to give some thought to producing the fine rod in a “steel” with handle etc.

[spydercolchester]

Hi
1- You should use the same type of knife with the same edge, steel type and blade type. 2 identcal knives one is a and one is b.

2- You should perform the test on many days doing the one test one knife, same time everyday. After cutting and sharpening for a while, your hand will feel weak resulting in weaker cuts. You will need to do 20 cuts to maybe achive the effect of 10 cuts if your arm was rested. :)

[Childe Roland]

Hi
1- You should use the same type of knife with the same edge, steel type and blade type. 2 identcal knives one is a and one is b.

2- You should perform the test on many days doing the one test one knife, same time everyday. After cutting and sharpening for a while, your hand will feel weak resulting in weaker cuts. You will need to do 20 cuts to maybe achive the effect of 10 cuts if your arm was rested. :)

I believe the knives tested were identical.

[spydercolchester]

true, I missread that.

[Senate]

interesting experience JDEE, thanks for sharing...
(and taking the time to do it :) )

[Stuart Ackerman]

Putting a weighing scale under the rope etc, will show how much more force is needed too. Thanx for the test, JDEE!! :)

[JDEE]

Putting a weighing scale under the rope etc, will show how much more force is needed too. Thanx for the test, JDEE!! :)

Carol has a set of digital scales she uses for weighing her wool which would be just right - but she won't let me use them. Looks like I'll have to buy my own.

Spydercolchester

Although it mightn't read that way the test was conducted over several days.

[mikewww]

Very interesting test. Thanks for that. Just one point, though. You make no mention of the tension on the rope. I believe it is easier to cut a taught rope than a slack one, so the test could be influenced by this. Perhaps one end could be in a vice and the other over a pulley with a fixed weight, of say 20 pounds. Also, how deep do you cut into the rope and what is its diameter ?

Otherwise, seems like a good practical test that anyone could replicate to compare blades, grinds and sharpening techniques.

Cheers

Mike

[JDEE]

Very interesting test. Thanks for that. Just one point, though. You make no mention of the tension on the rope. I believe it is easier to cut a taught rope than a slack one, so the test could be influenced by this. Perhaps one end could be in a vice and the other over a pulley with a fixed weight, of say 20 pounds. Also, how deep do you cut into the rope and what is its diameter ?

Otherwise, seems like a good practical test that anyone could replicate to compare blades, grinds and sharpening techniques.

Cheers

Mike

There is no tension on the rope, it is cut slack with Australian Hardwood as the cutting surface. This, as far as I know, the accepted rope cutting test. In my view cutting a taught rope could be dangerous. The cut is made through the rope, at about 1/2-3/4" from the tip and if more than one slice is needed of if the blade slips on the rope it is considered a failure. The rope is 3/8" manila.

[dialex]

Thanks for the infos. The results were somehow predicatable. The white stones gave a polish edge to the knife "A", while the gray stones put a coarse edge on the knife "B". You may consider the coarse edge as a multitude of microserrations. Therefore, knife "B" cut rope better, just as a SE knife is better at rope cutting than a PE.

[Mariner]

Thanks for the infos. The results were somehow predicatable. The white stones gave a polish edge to the knife "A", while the gray stones put a coarse edge on the knife "B". You may consider the coarse edge as a multitude of microserrations. Therefore, knife "B" cut rope better, just as a SE knife is better at rope cutting than a PE.

Agreed, but what I really found surprising from JDEE's test was just how much better. The difference was more significant than I would have anticipated. Thanks for sharing JDEE.

[talonturbo]

OK, so the microserrations are better for rope. But the next logical question would be...

Is there a cutting situation where a polished edge is the better performer?

Or does it simply make more sense to have all PE knives sharpened "roughly"?

[CKE]

I believe(not the gospel truth :) ) that a polished edge is better at whittling wood as opposed to a micro serration PE. Anything fibrous will be cut better by a SE or Microserrated PE. I think.....Take Care and Great Test JDEE!!!

[paulks]

I am not a cutting expert, but I remember reading some relevant info in an article on sharpening by Joe Talmadge (http://www.bladeforums.com/features/faqsharp.shtml):

[INDENT]Many treatises on sharpening tend to focus on getting a polished, razor-like edge. This is partially the fault of the tests we use to see how good our sharpening skills are. Shaving hair off your arm, or cutting a thin slice out of a hanging piece of newpaper, both favor a razor polished edge. An edge ground with a coarser grit won't feel as sharp, but will outperform the razor polished edge on slicing type cuts, sometimes significantly. If most of your work involves slicing cuts (cutting rope, etc.) you should strongly consider backing off to the coarser stones, or even a file. This may be one of the most important decisions you make -- probably more important than finding the perfect sharpening system!

Recently, Mike Swaim (a contributor to rec.knives) has been running and documenting a number of knife tests. Mike's tests indicate that for certain uses, a coarse-ground blade will significantly outperform a razor polished blade. In fact, a razor polished blade which does extremely poor in Mike's tests will sometimes perform with the very best knives when re-sharpened using a coarser grind. Mike's coarse grind was done on a file, so it is very coarse, but he's since begun favoring very coarse stones over files.

The tests seem to indicate that you should think carefully about your grit strategy. If you know you have one particular usage that you do often, it's worth a few minutes of your time to test out whether or not a dull-feeling 300-grit sharpened knife will outperform your razor-edged 1200-grit sharpened knife. The 300-grit knife may not shave hair well, but if you need it to cut rope, it may be just the ticket!

If you ever hear the suggestion that your knife may be "too sharp", moving to a coarser grit is what is being suggested. A "too sharp" -- or more accurately, "too finely polished" -- edge may shave hair well, but not do your particular job well. Even with a coarse grit, your knife needs to be sharp, in the sense that the edge bevels need to meet consistently.[/INDENT]
I remember Mike Janich demonstrating a "push cut," where the edge was placed on the target, then pushed perpendicularly to cut (without any lateral sawing motion). It's my untested assumption that a polished "razor edge" would do better on a "push cut," whereas a coarser "micro-serration" would be better for sawing cuts.

-- Paul

[dialex]

OK, so the microserrations are better for rope. But the next logical question would be...

Is there a cutting situation where a polished edge is the better performer?

Or does it simply make more sense to have all PE knives sharpened "roughly"?

Sure, each edge has is utility. For instance, I preffer to cut paper or strip wire with a polished edge, while for food preparation I'd rather use a coarse edge (I say "I'd rather use" because I already use a SE)

[JDEE]

A polished edge is useful in many situations. Wood is a good example whether it be whittling of chopping. A wood turner eg would have his/her chisels very finely polished. Another example is the good old straight razor. If you examine these tasks most of them involve some form of pushing where it is the weight behind the edge of the blade doing the cutting and not slicing action of the blade. The kitchen is a good example where you should have different edges for different jobs e.g. a small paring knife used to peel fruit, a larger knife used to chop vegetables should have a polished blade. Whereas a knife used for slicing meat or bread should have an aggressive edge. Of course there are a number of cross over areas where either edge will do the job.

[dinus]

In a SD situation what type of edge is best considering that you will encounter mostly skin but occasionally denim, leather, etc?

[paulks]

My limited and unscientific cutting tests have showed the straight and unserrated polished edge of Mike Janich's Yojimbo and Ronin cut the best for my potential urban SD situations. I carry a 2nd knife for everyday utility work, which ensures that my primary SD knife is always very very sharp.

[Blades]

What about a knife which one side is finished on the white stone, the other side finished on a grey stone?? :) Just being silly.
I like to sharpen the last inch or so of my knives(plain edge blades) on my ultrafine stone. That gives me a very fine edge for detailed cutting, but if I have to cut open a box, the rear of the blade is more "toothy". Or I just reach for my SE Endura. :)
If you don't have Joe's sharpening FAQ, downloaded on your computer, ya need to get it!! :)



Blades