Sharpmaker grit (medium/fine ceramics)

[Cliff Stamp]

A question was asked awhile ago about the grit of the Spyderco rods, I had been meaning to check this for some time, however I had given away to friends both Sharpmakers I had bought. Last week I was visiting and got a lone of one and did some testing to check the abrasives. This was a relatively new one which I had bought as a x-mas gift.

I used Olfa blades as stock to sharpen as I had ten idential blades which allowed for a quick comparison of repeated sharpenings. The corners of the rods were used to allow a consistent comparison against a standard fine DMT rod also new. The 15 degree setting was used to produce maximum tooth depth for ease of visual measurement.

Origionally I intended to just estimate the grit level of the rods by the finish they produced (the DMT is a known 25 micron), but then decided to do some sharpness and cutting comparisons as well.

The results :

http://www.physics.mun.ca/~sstamp/knives/sharpmaker_grits.html

-Cliff

 

[db]

Did you notice if sharpening pressure made a difference? Would it be fair to say the Spydy med is close to 1200 grit and the fine 2400? Good to see you found a way to give SOG a dig.

 

[Jeff Clark]

Nice test, well targeted to look for grit-specific effects. I was surprised at the order of the results for the poly slicing test. I would have expected to see benefit from the coarser finish, but the test showed the finer finish to be the winner. In a previous test you ran using a rougher edge finish on thin blades I thought you got the opposite results. Could you be using too much pressure on the blades such that you are still predominately in the push cutting arena? I suggest you repeat the test with lighter force.

While using the rod edges helps to isolate the grit cutting tracks for improved visibility I would not generally use a knife edge finished with the hone edges. I figure that the edge is subjected to a lot of local overstress when you use the hone edges. I would expect the edge to be less durable. I think you should try some performance tests using the flats of the rods. I would scrub the rods with sink cleanser before the test to get the most open grit condition. I would also finish with extremely light strokes to get the best edge allignment.

 

[thombrogan]

Originally posted by db
Good to see you found a way to give SOG a dig.

I didn't see it as a dig at SOG at all. A lot of companies make good knives, such as SOG, but don't sell them with good edges. Most of the consumers seem happy enough. Even Benchmade only recently got into the business of being consistantly sharp out of the box (whatever they're using on the newer knives makes quite a neat looking edge that's fairly sharp, but my older Benchmades all had hit-or-miss coarse-belt edges).

Cliff,

I wish I could get that tree-topping effect with my Sharpmaker (and every other abrading system I own/use). Great review.

 

[db]

Tom you may not be aware there is a history with Cliff and SOG. View the comment however you like, and I'll do the same. I am also interested in if there is a difference in the grit size if the flats are used compared to the corners.V

 

[thombrogan]

db,

My bad. I knew some knives he reviewed didn't do so well, but didn't think it extended further.

 

[Jeff Clark]

If you read Cliff's review SOG's navy seal style knife I don't see him "having it in for them". They just came out on the extreme end of the spectrum, "knives that don't cut well as they come from the factory". By reprofiling and sharpening the blade it would cut well. In the present review he wants to give readers a sense of the sharpness discussed and it helps to talk about a range of edges that they may have seen--from thin Spydercos on one end of the spectrum to thick and poorly done factory edges like you might have seen on a SOG combat/survival knife. Besides giving a point of reference for factory edges, it points out that you can usually do better than factory edges if you resharpen blades yourself. Sometimes you can do a LOT better. And this is true even if you are talking about reputable brands rather than made in Pakistan throwaways.

http://www.physics.mun.ca/~sstamp/knives/seal_2000.html

 

[db]

Sog sertainly isn't known for poor edges. In fact I think they are about average compared to most. So, Jeff I think your point is a good one, it's just SOG is a bad exsample. With that said factory sharpness to me is the last concern I have when buying a knife.

 

[Sal Glesser]

Thanx for the test Cliff. Spyderco extends a great deal of effort (time and money) to be able to provide our customers with very sharp cutting tools and a means to sharpen them. It's nice to know that the effort is occassionally noticed. Appreciate.

sal

 

[Cliff Stamp]

In regards to SOG, I used it as a low end for sharpness as that has been my experience with the NIB SOG blades I have used as well it has been clearly stated by SOG that the knives are *not* designed to push cut paper but only to slice paper at an angle - this is on the very low end for sharpness, far below the NIB standard for Spyderco. They have also pushed the knife myths of very sharp edges being weak and so on.

DB :

Did you notice if sharpening pressure made a difference?

In terms of scratch pattern, no. The abrasive depth here is about one micron and thus the difference in force from what is required to make a scratch to that which is necessary to drive the abrasive full depth is *very* small and thus you make the maxium depth scratch.

Jeff Clark :

If you read Cliff's review SOG's navy seal style knife I don't see him "having it in for them".

Yes, but you have to actually read the review to come to that conclusion.

[poly slicing]

In a previous test you ran using a rougher edge finish on thin blades I thought you got the opposite results.

I have done this before with more grits, ref :

http://www.physics.mun.ca/~sstamp/knives/vision.html#grits

As the abrasive gets too coarse it requires more force to slice on the draw, when finer it starts to be able to put cut through the poly and thus the slice becomes less of a draw. Note though that this is very material specific, 1/4" poly is very soft, a hard shelled "plastic" rope would give different results in favor of the more abrasive grits.

In the Vision chart the results fall off *fast* with CrO. Based on experience sinve that time, I now see that as having been significantly influenced by techinque, specifically edge rounding. If I get some time this week I may redo some blades with the fine Spyderco rods and then give them some work on CrO, say 5, 10 and 15 passes (or something similar) and then record the performance on the thread, poly and rope.

The interesting thing will be that while the polish will be raised on the edge due to the finer CrO, the sharpness will be degraded because the edge anignment and consistency will be down significantly because you are comparing freehand to basically a jig, and edge-into vs edge-training which is directly inferior.

I will also keep a lookout for some hard shelled rope.

[rods]

I figure that the edge is subjected to a lot of local overstress when you use the hone edges. I would expect the edge to be less durable.

Rods are among the worst sharpening implements in that respect because if you use too much force you can actually ripple the edge (like the much hyped brass rod test). Even if you don't visually see it bend, as you have note you can cause local defomations which lead to fracture with extended use. You have to be careful to exert just enough force to get the abrasive to just cut. With these blades this wasn't a problem because they are simple steels and thus easily machined and thus will hone under very light force so there is no danger of rippling. With steels like D2 I don't like rods and perfer flat stones as you tend to have to press really hard to get them to sharpen. Rods work best here if they are diamond abrasives as they cut under the least force.

I think you should try some performance tests using the flats of the rods.

I used the corners simply because I was comparing the edge to that produced by the DMT rod so wanted a direct comparison, not a flat ceramic vs a round diamond. It would be interesting to see though if you could get the edge sharper with the flats and if the scratch pattern was visually influenced, again this is dependent on the steel type and hardness as well.

I would scrub the rods with sink cleanser before the test to get the most open grit condition.

Yes, this was done.

thombrogan :

I wish I could get that tree-topping effect with my Sharpmaker ...

These blades have a primary edge angle which is very acute and thus the honing immediately set a micro-bevel that was a small fraction of a mm wide. This meant that you went from being very blunt (<10% of optimal sharpness), to full sharpness in just a few passes, thus sharpening is *very* fast. In addition they are easy to machine simple steels. Doing this without a micro-bevel on something like D2 would be *MANY* times more difficult.

Sal, no problem

-Cliff

 

[thombrogan]

Originally posted by Cliff Stamp
These blades have a primary edge angle which is very acute and thus the honing immediately set a micro-bevel that was a small fraction of a mm wide. This meant that you went from being very blunt (<10% of optimal sharpness), to full sharpness in just a few passes, thus sharpening is *very* fast. In addition they are easy to machine simple steels.

At the risk of sounding like Master of the Obvious or Broken Record Man, would the tree-tropping effect take one of these conditions?:

1. Really good sharpening skills. I can make a great edge with a Sharpmaker or an EdgePro, but not tree-topping great. Not knowing how to do it right may be hindering me.

2. A really acute primary angle, possible followed by a fairly accute microbevel. I'm guessing that the same sharpness required to get my .23" thick knife blade hair-shaving sharp would do even much better with a thinner edge.

Is that it? Is there something else? Thanks in advance.

Edited to add :

For the sake of sharpness, is the microbevel added because it's much quicker and easier to grind and polish?

Thanks, again.

 

[db]

SOG vs Cliff. Well I did read the review linked to by Jeff. My opinion hasn't changed. However, I don't wish to argue about it because it doesn't really matter to me. The Sharpmaker grit review is a good one and I had wondered like others what the grit is close to. I don't have a Sharpmaker but am assumeing that the Spydy bench hones are very close to the same.
Tom, I beleive the tree topping sharpness is mainly a edge polish efect, the angle may help some what but you should be able to achieve it with an angle of 22 degrees per side or less.

 

[Cliff Stamp]

thombrogan :

Really good sharpening skills.

Always help, but the Sharpmaker takes a lot of skill out of the equation. Very few freehand sharpeners could match a novice+Sharpmaker with a little instruction.

A really acute primary angle, possible followed by a fairly accute microbevel.

The more acute the edge angle the directly greater ease of achieving this level of sharpness because what you are measuring really is cutting ability and cutting ability is effected very strongly by edge angle. I shuold check a few blades at 20 degrees and check the difference in sharpness.

The first time I achieved it was on a ATS-34 custom which I had adjusted the edge angle down to <10 degrees per side. When sharpened the edge still had big microteeth (due to the grain structure and aggregated carbides) but still was sharper than anything else I had seen, going readily under 100 g on the thread.

I recently did it freehand with a knife with an edge angle of <10 degrees included. This I don't think indicates a high level of sharpening ability because the angle is so low the cutting ability is near retarted levels so even a halfway sloppy sharpening produces extreme results.

For the sake of sharpness, is the microbevel added because it's much quicker and easier to grind and polish?

It is a gadzillion times easier to sharpen a microbevel than the primary bevel (well this is a slight exaggeration it is about 1000 times easier for those that wish to nitpick). The difference is just the width ratio.

This is the principle behind the Razor Edge sharpening, and it is also mentioned in Lee's Book on sharpening. There is really no reason to not apply a secondary edge bevel outside of the purist cosmetic preference.

-Cliff

 

[thombrogan]

Originally posted by db
I beleive the tree topping sharpness is mainly a edge polish efect, the angle may help some what but you should be able to achieve it with an angle of 22 degrees per side or less.

It could be. I'll see what I can do to improve my technique at polishing. Right now, I can make hairs pop when the edge of the blade contacts the skin, but that's about as good as it gets.

Originally posted by Cliff Stamp
what you are measuring really is cutting ability and cutting ability is effected very strongly by edge angle

I think I see. Kind of like Gator97's test comparing a Strider fixed blade to a Benchmade fixed blade by slicing up cardboard. The Strider held its edge longer, but at .25" thick, it was eventually succeeded in cardboard cutting by a duller knife that was .125" thick. The difference would be the higher level of force needed to part the cardboard due to blade thickness versus the actual quality of the edge.

Originally posted by Cliff Stamp
The first time I achieved it was on a ATS-34 custom which I had adjusted the edge angle down to <10 degrees per side. When sharpened the edge still had big microteeth (due to the grain structure and aggregated carbides) but still was sharper than anything else I had seen, going readily under 100 g on the thread.

Poor little Sniper. What'd it ever do to you?



So, unless I insist, as I often do, that my blades look as pretty as a cup full sunshine, a belt-sander (or really coarse abrasive) and a Sharpmaker are all I need. For the knives that I want to keep pretty, a steadier, more practiced hand at the higher grits is in order.

Thanks, guys!

Edited to add:

So Lee and Juranitch's techniques are more about enhancing cutting ability than actual sharpening per se? They sound just on the cuff of being intrinsic. That is, sharpening is done so a blade will cut better, but you can have a polished edge that push cuts better or a coarse edge that pull cuts better or a coarse edge that outdoes a polished edge at push-cutting because the coarse edge is at 15 included degrees and the polished edge is at 46 included degrees.

Am I closer to understanding or do I need to lay off of the cough suppressant?

 

[Cliff Stamp]

thombrogan :

Kind of like Gator97's test comparing a Strider fixed blade to a Benchmade fixed blade by slicing up cardboard. The Strider held its edge longer, but at .25" thick, it was eventually succeeded in cardboard cutting by a duller knife that was .125" thick. The difference would be the higher level of force needed to part the cardboard due to blade thickness versus the actual quality of the edge.

Yeah same thing. Mike Swaim was the first person I saw to discuss this on the internet (years ago on rec.knves), specifially talk about sharpness and cutting ability as two different things and clearly noting that sharpness was just one element of cutting ability and how that thinner knives could appear to stay sharp longer simply because they cut better at a given sharpness. He was also one of the first to argue against the myth of sharper blades (and more acute edge angles) going blunter faster and argued for the opposite - which is in fact the case unless they are too readily damaged.

Poor little Sniper. What'd it ever do to you?

I actually broke the tip off that again just before x-mass, this is the third or forth time. It is now half the length it was, still a nice EDC blade though.

a belt-sander (or really coarse abrasive) and a Sharpmaker are all I need.

A belt-sander is great because it takes the labor out of the equation, you can take the edge down on even something like D2 in just minutes with no physical effort. Just buy a really cheap 1" one, unless you are actually making knives that is all you need. Get really coarse belts, 40 grit ZO eats through steel so fast it is amazing. Once you have that and start sharpening using the Sharpmaker to set secondary bevels it is a completely different experience. Sharpening becomes so trival that it is more difficult to tie your shoes.

-Cliff

 

[thombrogan]

Originally posted by Cliff Stamp
Mike Swaim was the first person I saw to discuss this on the internet (years ago on rec.knves), specifially talk about sharpness and cutting ability as two different things and clearly noting that sharpness was just one element of cutting ability and how that thinner knives could appear to stay sharp longer simply because they cut better at a given sharpness. He was also one of the first to argue against the myth of sharper blades (and more acute edge angles) going blunter faster and argued for the opposite - which is in fact the case unless they are too readily damaged.

Okay, so there can be the overlap where a gritty-edged Sub-Sniper can cut as well as a polished-edged a knife of a higher angle and an underlap where a .75" thick knife with 90 included degrees angle could have the most polished, aligned edge in the history of sharpening and still not cut most materials well. Light dawns on marble head.

Originally by Cliff Stamp
A belt-sander is great because it takes the labor out of the equation, you can take the edge down on even something like D2 in just minutes with no physical effort.

Tempting, but scary on two counts:

1. I destroyed a clip point trying to sharpen on one before.

2. I'm scared I'd end up flinging the knife into my head if it catches on the belt.

Still, if I'm going to get a gaping headwound anyways, might as well have something to show for it....

Originally posted by Cliff Stamp
Sharpening becomes so trival that it is more difficult to tie your shoes.[/B]

Which brings us back to the head-injury scenario.



It figures. Just as soon as I become interested in various waterstone-related media and strop accessories, the voice of Al Bundy reminds me:

"There's no mixup a sander can't fix up."

Well, that and my trusty Sharpmaker.

Lots to ponder....

 

[Cliff Stamp]

It does make it fairly easy to damage a knife cosmetically as the speed of metal removal is so fast, that is why I would do a lot of profiling on machetes and kitchen knives before trying something of any value. As for the injury, yeah that is a real factor, though not a very likely one. Using a pseudo-file made from coarse sandpaper is a pretty fast profiler anyway, it is just harder on the shoulder and arm. You can also try a dremel, not as fast as a belt sander, but will allow a decent hogging of the edge bevel.

-Cliff

 

[thombrogan]

Well, I guess that, ideally, the spine should be the edge bevel, so that it'd make items like the sander, Dremel, or coarse-papered sanding block good to have and then the very edge would be brought out almost instantly with the Sharpmaker.