12-14-2018

Sharpening Knives - the Spyderco Sharpmaker

I have a Sharpmaker, like it a lot, and highly recommend it. It is a lot of bang for the buck at approximately $60 for the unit.

People say it should be called "Sharpkeeper" because it is really for keeping sharp knives really sharp. Sharpening a dull knife will require a bench stone or the diamond rods to get started.

An interesting fact is that Spyderco began their business with sharpening equipment and got into knives later, so they ought to know what they are doing.

In the above "Sage" forum discussion, one fellow says that he would trade the fine rods for a pair of diamond rods if he could own only one pair of rods. He says he can get shaving sharp with the coarse (brown) rods. He also says that the ultrafine rods are a novelty if you want hair whittling sharp results.
The whole discussion above is very much worth reading.
Note that the Sage 1 has S30V steel, nothing wildly exotic.

Here are some of the ten rules:

Along with the Sharpmaker, I purchased the diamond rods as well as the ultrafine rods. The fine and ultrafine rods are both white. The ultrafine rods are painted red on the ends.

Some words about the Sharpmaker rods.

The basic setup comes with two pairs of rods - coarse (brown) and fine (white).

Note on the video that it is recommended to "crack" the brown rods by rubbing them against each other before starting to use them. I guess I missed that part.

Note that these grit and micron numbers for the sharpmaker rods are "bogus". In actual fact, all of the ceramic rods are made from a nominal 15 micron material and are given a different surface finish. In other words, the grading of the stones is based on surface texture rather than grit of the component material, which makes complete sense if you think about it.

As far as the diamond rods, I compared them under the microscope to a known set of 180 and 400 plates I have, as well as to SiC wet/dry paper. I am satisfied that 400 grit is about right, although some people have claimed 220 - maybe this was on some older version of the rods. Who knows? So far I have used only the flat side of the diamond rods to reprofile some of my knives, and this has worked rapidly and well. The main thing with either diamond or CBN is to go light. Use virtually no pressure at all and you will get better results at the same speed and will avoid tearing the diamonds out of your rods.

Although the "official" instructions recommend starting with the corners of the rods, this is because the rods will cut faster due to increased pressure on a smaller area. Many users use the corners only for serrated blades. If you need to remove a lot of material (i.e. reprofile a blade), use the diamond rods.

Sal Glesser - 2007/12/30
... All of the ceramics use the same micron size (15-25). the different grits are created by different carriers, different firing techniques and diamond surface grinding.
Sal Glesser - 2007/12/31
... Most abrasives are measured by the grit size used in the matrix. Our ceramic doesn 't work that way. Grit size is constant.
The diamond stones are for rapid material removal when it becomes desirable to reprofile a blade. Some people are not satisfied with the speed even with these and use either a diamond lap propped up at an appropriate angle or even 100 grit wet/dry silicon carbide paper wrapped and clamped to a sharpmaker stone. The diamond rods have worked fine for me. Don't press too hard, that will only serve to wear out the rods prematurely by scraping diamonds off of the rods.

Diamond versus CBN

Here are some words from Sal (on the Spyderco forum in March, 2018) about the CBN rods for the Sharpmaker:
We've been making diamonds for our Sharpmaker since 1981. Even before we had the medium grit stones, we had diamond sleeves. When we could, we made diamond triangles. The problem with diamonds is that they are attached to a steel embryo using a plating process. The diamonds are very hard. Harder than the steel embryo or the plating material that adheres the diamond to the steel. People using the diamonds to sharpen will generally press too hard, which loosens the diamonds from the plated material so longevity is not as desired. Diamonds work best with a very light touch, as the diamonds are much harder than the blade, it doesn't take much pressure to be effective. Getting customers to do this has been very challenging. Most people think (or simply intuit) that "if I press harder, they will cut faster".

CBN has some advantages over diamonds in cutting steel and it is hard enough to sharpen any steel, I felt that if we made our triangles in CBN as well as diamonds, people could try both and in time we might see a difference or advantage to one or the other.

I use CBN and I also use diamonds, but I use a very light touch and take the time to do a careful job not to damage the diamond / CBN. I believe that the CBN might be competitive in that it cuts as well, and I believe adheres better to the plating.

The CBN rods are reputed to be 40 micron (about 400 grit), which would be less coarse than the diamond.

Bench stones

For a truly dull knife, forget the Sharpmaker. Reprofile the edge on a bench stone of some kind. But don't wreck the stone by using too much pressure:
Diamond hones from reputable makers (DMT, Eze-Lap, Lansky, Gatco, Spyderco, etc.) generally will only wear out prematurely for one reason: using too much pressure, which rips the diamond particles out of the nickel substrate. Diamond hones will always go through a 'break-in' process, and will feel smoother to the touch with some use. The most difficult thing for most people (including me) to learn, about using diamond hones, is just how light the pressure can be for the the hones to be really effective. Diamond is so much harder than the steel, and will rip through it with little pressure applied (see how little effort it takes to scratch a polished knife blade, with an accidental feather-light brush against a diamond hone). Some 'simpler' low-alloy steels will feel almost buttery soft on a diamond hone. A burr can be created very quickly on these steels, using a diamond hone, and can also be erased in a single pass. I've done this, and it makes it very hard sometimes to detect the burr, if you're not watching very closely; it's there, then it's gone. So applying too much pressure is counter-productive most of the time anyway. Some of the high-alloy steels, like S30V, will be a little tougher on diamond hones, if too much pressure is used. It's not the steel being tougher/harder than the diamond, but the steel in relation to the holding strength of the nickel substrate, which is limited in it's ability to hold onto the diamond particles. Using too much pressure with more abrasion-resistant steels will only do more damage.

Keep the pressure LIGHT, and your diamond hones will be OK. Keeping them clean will also reduce the temptation to 'bear down' a bit, if the hones are getting clogged and ineffective.

Videos

The sharpmaker ships with an instructional DVD. You should watch it (you can find it online, which was more convenient for me that finding a DVD player. My sharpening improved when I did as the instructions say. (How about that!) I sharpen standing up and hold the knife with my thumb on top. Find a bench or table about waist high to put the sharpmaker on. I learn things from the jdavis882 videos, but you have to be patient as he goes slow and tends to repeats himself. He recommends the leather strop from Knives Plus for finishing after using the ultrafine stone on the sharpmaker. So, do you use the rods at 30 or 40? It depends. If you want a really sturdy edge, reprofile to 40. I do not intend to do this.

Most Spydercos come from the factory sharpened quite precisely to 30 degrees. Some people simply stick with this. Some steels may not support an edge this acute. Generally though, the 40 degree setting just for setting a microbevel. A couple of strokes at 40 with almost no pressure will accomplish this.

Some heavy use fixed blades come sharpened to 40 inclusive, and maybe this is just right for such knives.


Feedback? Questions? Drop me a line!

Tom's Knife Info / tom@mmto.org