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Whetstone Grit

Whetstone Grit

You can use natural or synthetic stones, grinding discs, special plates, and even sandpaper to sharpen knives. All of these tools have one important specification: grit (mesh, in some sources). 

The impact on the steel of the blade depends on this specification. The coarser the grit of the abrasives, the more steel they take off the edge. This treatment is too coarse, and the knife edge surface needs to be polished afterward. Due to this, craftsmen and professionals use a set of multiple stones of different grit. 

Let us take a closer look at what the grit is, in what units it is measured, and how to choose a sharpening stone for use in a personal or professional kitchen or workshop. 

Features of sharpening stones

Using an abrasive whetstone is a manual knife sharpening method that is popular among fans of high-quality products. It can be natural or synthetic. 

The blade sharpening process involves using the hard abrasive particles that make up the stone. They are bound together with special materials that determine their hardness, wear resistance, and service life. 

How to choose a whetstone

You need to pay attention to several factors when shopping:

  • Manufacturing material. Whetstones can be made of rocks, ceramic materials, diamonds etc. This determines the impact on the blade, the service life of the stone, and the time it takes to sharpen a knife. 
  • The grit of the whetstone. Particle size affects the quality and accuracy of the finish, as well as the amount of metal the stone removes in a single pass.
  • Sizes. The size of the stone determines the convenience of sharpening blades of certain sizes and the service life of the stone itself. 

Let us analyze each of the specifications. 

Material of stone manufacturing

You can find several types of sharpening stones on the market. 

Water

Whetstones are made of natural or artificial abrasive materials. The first are made from rocks that are only mined in certain regions of the world. The most popular natural stones are made of rocks extracted in Arkansas, USA, and Japan.

The second ones are made of aluminum, silicon, or chromium oxides. First, they make particles of the required size using a sophisticated technological process, after which they are bound together with a ceramic or bakelite-based binding agent. 

The term "water stone" comes from the way the sharpening stone is used. Before use, you have to soak the stone in water until the liquid fills all the pores. During the process of restoring blade sharpness, you have to keep the surface wet all the time. This forms a slurry which consists of abrasive, liquid, and metal particles from the blade. Thanks to the slurry, you get a uniform sharpening of the edge along its entire length. 

The impact of the stone on the knife's steel alloy depends on the size of the abrasive particles, and the grit. The coarser it is, the more steel the bar will remove from the blade. This causes the edge to develop defects (e.g. scratches) that need to be removed afterwards. 

Silicon carbide for sharpening stones

Diamond

A diamond sharpening stone can serve as an alternative to a water stone. A special feature of diamond abrasives is their high hardness. They scrape off the material and allow you to shape the edge. 

The features of manufacturing diamond-coated stones allow you to make them with different grits. All particles will have 1 grit size, which increases the sharpening quality. Diamonds are sprayed in a thin coating on a solid base for convenient use. These stones are often used with sharpening systems that allow you to adjust the sharpening angle. 

Because of their increased hardness, these stones have a very aggressive impact on the steel surface of the blade. Due to this, they allow you to quickly restore the sharpness of the knife blade. However, there is a risk of damaging the steel if you do not handle it properly. Diamond sharpening stones reduce the life of the knife, so it is better to use medium to fine grit diamond stones.

Unlike "water" stones, you do not have to wet the diamond surface with water. Just rinse after use to wash off any remaining metal residue. 

Artificial diamonds for sharpening stones

Ceramic

It is a type of synthetic sharpening stone that has a soft impact on the edge. This helps you to avoid damaging the blade during sharpening. Thanks to the ease of machining raw materials, manufacturers offer products of various sizes and shapes, which you can use to sharpen knives, scissors, fishing hooks, and other cutting tools. 

There is no need to wet the ceramics with water to create a slurry. But you have to wash it after sharpening to avoid the accumulation of steel particles removed from the edge. 

Whetstone grit

After choosing the material of the bar, pay attention to its grit value. It determines the degree of impact on the knife you are going to sharpen. 

This specification is regulated by several standards, and different units of measurement are used for its designation: FEPA-F, FEPA-P (sandpaper), microns, and other grit standards. The approximate value conversion and the purpose of the stones are shown in the chart.

If you use a stone with too coarse a grit, it will take off a lot of metal and leave large scratches and grooves on the blade. For most types of knives, this sharpening quality is unacceptable. High-quality work implies a complete absence of defects. Stones of this type are only suitable for coarse work when you need to repair heavy damage. 

Fine grit stones allow you to smooth uneven parts of the edge and make the blade razor sharp. But the abrasive particles of fine grit stones only remove tiny bits of steel in one pass, which makes this kind of work time-consuming. 

The best way is to use several stones with different grit, 1 grit at a time. The sharpening process should start with the coarsest stones and gradually move to finer stones until you get the best blade finishing. 

Grit
class

Average
particle
size, µm

JIS
R6001-87
(water stones)

ANSI
B 74-12,
B 74-10

FEPA
32GB,
33GB

GOST
9206-81 (diamonds)

GOST 3647-80 Purpose
14 0.025 0.1/0 Honing and polishing, super finishing
14 0.05
13 0.07 200.000
13 0.1
12 0.15 100.000 0.3/0
12 0.25 60.000 100.000
11 0.49 30.000 60.000 1/0.5
10 0.74 20.000 20.000
10 0.91 16.000 16.000
9 1 15.000 14.000 1/0
9 1.2 12.000 13.000 F 2000 2/1
9 1.5 10.000 10.000
9 2 8.000 F 1500
8 2.5 6.000 9.000 3/2
8 3 5.000 8.000 F 1200
8 4 4.000 5.000 F 1000 5/3 M5
7 5 3.000 4.500
7 5.3 7/5 M7
7 6.7 2.200 3.000 F 800
7 7
7 7.2 10/7 M10
7 8.5 1.800 P 2500
6 10 1.500 F 600
6 10.3 P 2000 14/10 M14
6 13 1.200 P 1500 F 500
6 14
6 15 1.000 P 1200 20/14 M20 Removing scratches
6 18 800 P 1000 F 400
5 20
5 22 700 P 800 F 360 28/20 M28
5 26 600 P 600
5 28
4 30 500 P 500 F 320 40/28 M40
4 35 400 P 400
4 40 4 Removing signs of coarse sharpening, sanding
4 41 360 P 360 60/40 M50
4 46 320 P 320 F 240
4 50 5
3 53 280 P 280 F 230 M63
3 58 P 240 F 220
3 68 240 P 220 F 180 80/63 6
3 77 200
3 82 P 180 F 150 8
2 100 P 150 125/100 10
2 125 P 120 F 100 12 Coarse sharpening, intense metal removal
2 136 120
2 185 F 80 16 = 160 µm
1 260 P 60 F 60 20 = 200 µm
1 310 F 54 25 = 250 µm
32 = 315 µm

Grit measurement unit

Despite the difference in the designation of abrasive grit in different standards, knife sharpeners, and knife enthusiasts have come to a common agreement and designate this value in grit. The smaller the number, the larger the abrasive particles will be. For example, a 120 grit stone has large abrasive particles and is only used for coarse sharpening. Finishing and polishing work is carried out with 1200-8000 grit stones.

Some of the standards follow the same logic, such as FEPA-P (sandpaper) and FEPA-F, while the others have a different pattern of grit change, such as the micron (GOST) standard. You can see the approximate FEPA-F to micron conversion in the aforementioned chart. 

Which grit to choose 

People choose the grit of the abrasive stone depending on the type of knife they are going to sharpen and its purpose. For most knives, experts suggest the following stones grit:

  • 120 grit - coarse sharpening to remove excess steel and shape the cutting edge profile;
  • 1000 grit - for final edge alignment and removal of small scratches;
  • 2000 grit - for finishing knife blade polishing. 

Stones grit

The first two stones will be enough for most kitchen knives. The last one is essential if you want to have the best finishing of the knife blade. 

The main point is to use sharpening stones in a strict order from coarse to fine. And you should increase the grit value 1 grit at a time, without skipping even 1 grit step. 

That is, you have to first take a 120-150 grit stone to remove large defects and set the angle. After that, use a product with fine abrasive particles that will remove scratches and smooth the edge. 

Note, if the markings on the stone are in micron grit standard, you have to gradually increase the value (see the chart for more additional information). However, for some sharpening stones manufacturers use mkm to specify the grit. In this case, you have to do the opposite. That is, 100 / 80 for coarse sharpening, 3 / 2 for sanding or polishing.

The number of sharpening steps depends on the amount of stones with different grit that you have. You can follow the pattern of 150-250-500-1000 … 8000 and so on. Fine grit sharpening stones cannot remove defects left by much coarser grit sharpening stones, which is why it is important not to skip steps. Or the whole sharpening process will take too much time. 

It is important to understand that a complete knife sharpening with a whetstone or a sharpening system is something that should be done only rarely. A knife should get a complete sharpening once or twice a year, depending on how often you use it. In the meantime, you should hone the edge. People use musats (honing rods) for this purpose. This is why sharpening stones last a long time, despite the rapid wear of natural and ceramic abrasives. 

The size of the whetstone

The important specifications of the stone are the width and length of its surface, as well as its thickness. The first two specifications depend on the dimensions of the blade:

  • large stones, 21 cm long and 7 cm wide are suitable for knives with a blade length of 20 to 26 cm;
  • The smaller stones, 17 cm long and 5 cm wide, are suitable for sharpening knives with a blade up to 15 cm long. 

Stone length to blade

The stone's thickness only determines its convenience of use and service life. As the surface gradually wears away, the larger the stone, the longer it will last. 

Diamond plates as an alternative to stones

Choosing sharpening stones, and using and caring for them properly is time-consuming and requires some skills. But some manufacturers offer an equally efficient substitute. 

You can sharpen your knives quickly and properly with the diamond coated plates from TSPROF. Hard diamond abrasive particles quickly grind metal off the cutting edge and remove damaged parts of the blade. The set includes five stones with grit from 150 to 1000 (FEPA-F), which is more than enough for household or kitchen purposes. You can continue polishing the knife edge with any additional natural or synthetic stone of 8000 or other grit value (higher than 1000) if needed.

They do not need to be wet or otherwise prepared for use, just rinse with water after use. You can use these diamond stones on a backing plate in combination with sharpening systems that allow you to set and maintain the desired sharpening angle or on their own - for manual sharpening with a whetstone.

TSPROF Diamond Plates

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