The stones to sharpen and their “grains”

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These days I’m doing a search to change the sharpening stones that I have because they are not of quality and I realized that it was money not spent well so I decided to share with you my ratings.

Let’s see what the abrasives commonly used to sharpen and their grains are based on.

This technical topic is very important for a maker because the last stage, that ofsharpening is complex and it is not easy to achieve satisfactory results at 100.

Grain is the degree of roughness ofthe stone, and is an indication of greater or lesser aggression and as for the abrasive tapes of the sander or the common sandpaper that you use in finishing, the lower the indicated number and the more abrade.

Now, however, it is not said that an aggressive grain must necessarily abrade faster, since this is given as well as by the grain also by other factors, such as:

  • hardness in hrc,
  • composition,
  • et cetera.

An example, for the same grain, the maamated stones, for example, abrathe faster.

The stones are divided into 5 macrogroups:

OIL STONES

This includes the natural American Arkansas, european Coticule and Belgian Blue, which are stones high in silica and can be used for the final sharpening phase being very hard.

They are quite expensive, and being natural, they are becoming increasingly rare.

Among the most common oil stones, there are also those made with aluminum oxide (such as Norton India) that are suitable for everything and make a great thread, and those with Silicon Carburo (such as Norton Crystolon) that are little softer than diamond and abrasive faster Mind.

With use, they are consumed and need to be rectified.

There are in various grains, they can also be used on knives with HRC close to 64 degrees Rockwell.

Although each type has soft, hard, etc., let’s say that a true ranking for uses is this:
  • Stones with silicon carb for a fast wire or for very hard steels.
  • Aluminium oxide stones for a sharper and more precise thread, and a little for everything.
  • Natural stones Arkansas for the last step and for very shiny wires.

Pregi: Low cost, with 10 euros you can sharpen a razor knife.

General defect of oil stones: is that it is the slowest type, they abrasive slowly, and the use of oil is a bit of a break.

JAPANESE WATER STONES

By now there are no more natural stones, and they are all human work stones, they are composed of silica particles (generally aluminum oxide) mixed with a clay matrix.

The stone is “soft” as the particles have a bland bond and wear out quickly, this is the great value and the great defect, as it makes sure that there is always new material that can work perfectly and you create a dough with water , which polishes the wire, however go after some adjusted use.

They are used with water.

The merits of this type of stone is that they abrature faster than oil stones, and at the same time polish the thread, years of sharpening of Japanese katane teach, a great experience and use with water is simpler and cheaper than oil.

As “defect” they have a high cost, they are consumed quickly and need to be rectified.

SECCO DIAMANTATE

They are practically metal slabs with diamonds attached to them, which is the hardest material in the world, there are many grains and they have many merits, including the speed of sharpening, the fact that they can work even dry and do not wear out, the defects instead is that in some cases the diamanate particles can detach from the support and that being very abrasive, you can easily damage the wires.

Merits: There is no steel that is not abrasive by these stones, if you have major damage to the wire, they are very quick to restore it

Flaws: Not all the dits are quality, they cost enough, and someone says that you do not have the same feeling as with natural stones.

CERAMIC STONES

They can also be more or less fine, but they are used in most part for the final phase of sharpening, having very fine grains, very hard material and that consumes very little, comfortable are the sticks, with which you can also sharpen the serrated blades.

They are used dry.

SYNTHETIC STONES

Used mainly in small sharpening kits, there are the various stones in Tungsten’s Carburo, a very hard material suitable for fast abrade but that leaves a somewhat coarse finish, used for very hard steels; those in Aluminum oxide, very common, suitable a little for everything, Silicon Carburo, used mostly for roughing and repairing the hard-damaged wires, given the aggressiveness, is a hard material just under the diamond.

They are used dry or with oil.

STROP AND COMPOUND

This is an intruder genre, which has nothing to do with stones, but since it is still used for the same purpose, I insert it, practically they are pastes to be passed on the leather to sharpen and polish the wire, they have a limited degree of abrasiveness, some they use in place of the pastes, directly the sandpaper put on a perfectly flat stand like a ceramic tile.

THE GRANEs

This is a summary of the grains for natural stones:

  • Grain 240-400: great for roughing and aligning the sharpening
  • Grain 800: to optimize the wire
  • Grain 1,000: to liven up the thread
  • Grain 4,000- 6,000: they guarantee you shiny wire

Ps. Beyond these grains you go in to truly levels that also require incredible skills or in the paranoid, remember that however only with quality steels the thread of the knife can be brought to this degree.

These are the nomenclatures of the damanted stone grain DMT (famous house of diamanate stones), but it applies more or less to all the diamanta stones:

  • Extra-Coarse diamond (60 microns / grain 220)
  • Coarse diamond stone (45 microns / grain 325)
  • End diamond (25 microns / grain 600)
  • Extra-Fine diamond (9 microns / grain 1,200)

To which are added these compounds for strop in syringe:

  • Copper-colored syringe (6 microns / 4,000 meshes)
  • Yellow syringe (3 microns / 8,000 meshes)
  • Grey syringe (1 micron / 15,000 mesh)

Ps. A special mention is for the DiaSpray spray, which equates to 0.5 microns, or about 30,000 grains, water and finger particles, we are in science fiction!?

 

These are the classic compounds for strop:

  • Coarse – Black compound (100 abrasion)
  • Medium – compound White (50 abrasion, 50 polishing)
  • End-compound Green (25 abrasion, 75 polishing)
  • Finer-compound Red (100 polishing)

Conclusions

My final choice was to water stones and diamanta stones, I wanted to try both solutions going to replace my old water stones with higher quality stones.

I didn’t consider the oil ones, but it was my personal choice.

I hope this research will be useful for your personal choice.

Good hand sharpening!

Andrea


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This post is also available in: Italian

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