The Sharpmaker vs. surface area

J

JohnW

Joined
Sep 11, 2000
Messages
144
I've been using my trusty Sharpmaker 204 for a year and a half now, and have been extremely happy with it. It is worth every penny of the cost. If you are in doubt and still considering one, there's no need to wait. It's great alone, or as a complement to any other system. That said, it is not the be-all and end-all of sharpening. By any means.

As I find myself venturing further afield into the domain of sharpening, learning new things about every few months, I'm starting to tackle bigger and harder projects. This week I'm reprofiling a friend's light duty folder to a more aggressive slicing edge (he mainly cuts string and tape, no cardboard or rope).

The blade is well-hardened 440C, and came with a 20-22 degree bevel. I'm currently regrinding it to a 15 degree bevel, planning for a 20 degree roughened micro-bevel. It will make the blade much weaker than it currently is, but my friend's usage patterns justify the increase in slicing ability vs. edge durability (and longevity).

To do the reprofiling work, I've mounted a DMT medium stone to one of my Sharpmaker ceramic stones (1/8" cord and a "constrictor" knot [see any knot book] are very handy for stabilizing this setup). You cannot, I repeat, absolutely cannot reprofile a hardened steel blade on a Sharpmaker. Humans just don't possess enough patience. The problem is not that the stones aren't hard enough; they're plenty hard. It seems to be a problem of surface area.

Just for kicks I tried reprofiling this blade using the edge of one of the medium ceramic stones. In the beginning, it started to wear away the old 22 degree shoulder pretty quickly. I kept watch using a bright light and a 30X magnifier, and could see the new bevel getting wider and wider every 10 strokes. Then every 50. Then every 100.

By the time the new bevel was about 60 percent the size of the old bevel (it's hard to explain without a picture, but basically I'm 2/3 of the way there), it was necessary to apply 300-500 strokes to see any noticeable change. To fully establish the new bevel, at this rate of geometric increase, would probably take 10,000-50,000 strokes!!

That's just a guess, but consider what's happening: the steel I want to remove is basically a long, flat triangular bar attached to the side of the knife. Removing that bar will leave me with my nifty new bevel. So every grain of steel in that bar needs to go.

When I first started out, I was wearing away the top of the bar, which represented a very narrow band. But as I wore away more and more, the number of grains next to remove (the surface area presented to the ceramic surface) was increasing dramatically. By the time the new bevel was near the edge, that's a fair bit of steel! And those ceramic sticks charge up so quickly... Even with a lot of Comet on hand, it takes a very long time.

So I switched to the medium DMT, and even though it still took several hundred strokes, I was able to establish the new bevel. Keeping close watch on my progress under magnification made it possible to grind the bevel reasonably regular and flat, but by no means perfect.

All this, though, has led me to a question: when I finally establish my nice, 15 degree, flat bevels, how is my Sharpmaker ever going to resharpen them? That is, for every *grain* of steel I lose from the edge, I will have to remove one grain from the entire surface area of the new bevel. If I wait a little while and let the edge blunt even a little bit, this means a veritable micro-sheet of steel will have to come off to keep the edge truly sharp.

Which is why it seems the Sharpmaker was designed for double-bevel edges. With a double-bevel, where the primary bevel represents the vast majority of the edge's surface area -- and which does NOT need re-grinding in order to resharpen -- the Sharpmaker only has to grind away grains from the very narrow secondary bevel, which the ceramic rods can handle just fine.

Is the Sharpmaker totally inadequate for acute, single-bevel edges? It's a great system for doing touch-ups, maintaining double-bevel edges, and creating micro-bevels; but will I have to go to something like the Edge Pro to keep this 440C blade sharp with the least steel removal?

Wondering, John
 
John,

I find most of the production knive I've bought have asymmetrical bevels. That is, one side includes and angle that is, say, 19 degrees off the axis of the blade. The other may be 23 degrees. Sometimes, I find, naturally, that the total included angle of the bevels is something other than 40 or 30 degrees.

So, I always end up having to reprofile in order to take full advantage of the Sharpmaker. But it is slow and I spread my reprofiling out over a couple or three days to keep from getting too frustrated. Once you're profiled to match the tool's 30 and 40 degree total included angles, you're set.

Also, keep in mind that steeling and light touch-up sharpenings may keep total sharpening effort down some. And, now you can buy diamond stones for the 204 for about $50 and that may speed things up some. I may try that some day.
 
When it comes to any reprofiling, you're not going to do much better than DMT stones. If you learn to do it freehand, just lay the stone on a table and slide that blade across it again and agains and again, you'll get the job done pretty quickly.

As far as resharpening once you get that single bevel, I have a puukko that came with a razor sharp single bevel, and I fumbled my way through many years of keeping it fairly sharp. Once I got the Sharpmaker, the job got easier, since I only have to touch it up with the edges of the white rods at thirty degrees. Yes, this puts a tiny secondary bevel on it, which was easy to do and is easy to maintain. (It push cuts through stale bagels :D )
 
JohnW, That is the most accurate description of the sharpmakers limitations I have read to date. Thank you!

I have read many, many sharpening articles trying to increase my skills in this area such as you have. I had found the exact same problems with the sharpmaker that you did. My lightbulb went on when I obtained a REKAT Hobbit Fang neck knife. I wanted to reprofile the edge to 12-15 degrees per side from it's original 20-25 degrees. My thinking was, if I'm ever going to use this knife, ( I always have at leat 3 knives on me), I want it to be razor sharp to cut cloth and or flesh in one swipe. I have utility folders in my pocket and on my belt that are double beveled and sharpened @ 40 degrees total on the sharpmaker. This works great and lasts quite a while for cutting rope, cardboard, wood, rubber & plastic. The Fang has an entirely different function. If I've had to "whip it out" It NEEDS to slice right thru in one pass.

I tried to acheive this reduced angle bevel on the sharpmaker and after about 100 stokes on side 1, I began to notice the problem. One thing that helps for sure is cleaning the stones. When reprofiling a hardened steel whether it be high carbon or stainless, your taking off quite a bit of the metal. that metal is deposited in the pores of the ceramic. After about 20 strokes on the corner of the medium stone, it's cutting ability begins to decline greatly. You can turn the stones 3 times till you've used up all the surface but then you must clean them or you are wasting your time. Using the flat side of the stones works but takes much longer than the corners.

I have found that a Lansky system with diamond stones works much faster and with a little more geometric accuracy than a free hand sharpmaker for reprofiling a blade. The sharpmaker WILL work but it takes longer and you must clean the stones frequently. I now do all reprofile work on the Lansky and I use the Sharpmaker for the second bevel or on single bevel knives cut at 40 degrees. I have not tried the diamond stones for the sharpmaker but I suspect they will be a big improvement for this type work.

Currently, I'm trying to master fixing points that have been rounded off by my mistakes while learning this craft. Other members have suggested and I have proven that letting the knife blade come off the corner of a Sharpmaker's stone at the bottom of your stroke WILL round off the tip. It doesn't matter of the tip travels off the stone on the downstroke on the flat side of the stones, only on the corners. What happens is, you apply pressure towards the stone your using and as you pop off the corner of a stone, your brushing against the flat side with the tip of the knife. I didn't notice it for quite a while but after several sharpenings, it was too late. Putting back the needle point has proven to be a challenge for me. When I get that mastered, I'll let you know.

3 items that are indespensible for sharpening for me are; bright lite, black magic marker, and a 10X jewlers loop. If you had one of those magnifying benchlights that would work very well also.

Good luck!

Greg
:)
 
Jay and John,

Originally posted by JayBird
John,

...
And, now you can buy diamond stones for the 204 for about $50 and that may speed things up some. I may try that some day.
Click to expand...

I can attest that does work very well. I have one of the older Spyderco sharpmakers. It came with two diamond-coated sleeves that slide down over the triagular stones.

If I am sharpening a new knife with the Sharpmaker, I always use the diamond sleeves first until I get the new edge angle established...saves mucho time!

--gordon
 
Can someone point me to where the new diamond rods are available for $50? I've only seen them for twice that amount. TIA.
 
The 204 is slow to reprofile with.... but the good news is that for the initial steps of the reprofile you are just trying to remove a large amount of metal, so the angle does not have to be as consistent as in the later stages.
I take a big ezlap diamond hone (11") and grind away at the approxomite angle (usually 15-20 degrees depending on the knifes purpose), Then after the vast majority of the "excess" metal is removed I switch to the 204, to align the edge, make the bevels symeterical and to finaly polish.....
This is what works for me......

My intelligence level is somewher between idiot and moron (based on IQ) but my knives are sharp,,,,,,,,,,,


BTW this prior posts have been very well written and show an understanding of edge geometery that is refreshing.....


Take care,
Chad
 
JohnW :

when I finally establish my nice, 15 degree, flat bevels, how is my Sharpmaker ever going to resharpen them? That is, for every *grain* of steel I lose from the edge, I will have to remove one grain from the entire surface area of the new bevel. If I wait a little while and let the edge blunt even a little bit, this means a veritable micro-sheet of steel will have to come off to keep the edge truly sharp.
Click to expand...

The length that the hone has to pass along ideally has no influence on the depth of the scratch that it makes as it will cut a consistent depth scratch pattern along the entire length. In practice though, there are two main factors which cause this not to be true. The first and most important is that the wider the bevel the lower the pressure for a given force.

When you started off you were just hitting the shoulder and thus the force was all concentrated at one point and the pressure *very* high. As you progressed the contact area ratio became very small and thus the pressure scaled the same way. You can counteract this just by using more force.

The other factor is as mentioned in the above, after each pass the hone is loaded with steel and thus is less aggressive. Unless you clean the hones periodically you will see a significant drop in aggression.

All hones and sharpening systems have these problems to some extent. Japanese waterstones are the least effected as you can lean on them really hard with no problems and they are self-cleaning because of the breakdown of the abrasive and the flushing of the water.

Anyway, back to your question, as long as you keep the blade decently sharp, it can be restored with just a few passes on a hone as you only need to remove less than 1/10 of a mm of steel and you can do that with just a few passes.

However your point about double beveling is very sound. It allows a a much quicker sharpening with very little loss in cutting ability. Every once in a while you just recut the full bevel on a coarse hone to make sure that the secondary bevel doesn't thicken too much. Double bevels also have durability advantages as well, same as convex bevels.

-Cliff
 
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