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PT Recommended selections of sharpening stones: diamond and cubic boron nitride sharpening stone sets
How to select sharpening stone
Common issues:
- Abrasive grains are covered with bond after sintering, so you may need to remove the layer of a bond to release abrasive grains (to break stone).
- Fine grain sizes (below 5/3 micron) may form aggregates which leave scratches. So you may need to dress these stones more frequently to remove aggregates out of the bond. We guarantee no aggregates for grain sizes 2/1 micron and coarser.
- Edges of abrasive layer may appear too sharp after sintering, so you may need to flatten them.
- Sharpening stones with coarse grain size (>125/100 micron / Grit 140) may look uneven. We prepare(polish) them for the first use and grains released from bond may create such appearance. This is normal and no need to flatten surface. All stones are checked for flatness before shipping.
- 200% concentrations stones may seem to wear off faster (shedding of abrasive grains), but this is just because their productivity is also much higher.
Select at least one metal bond stone with coarse grain size (100/80 and coarser) for a set of combined bond (resin bond) stones. This will increase total tooling life.
Italian black slate and polishing pastes
Italian black slate hardens cutting edge, pastes provide mirror polish and can be used after slate if you need this appearance.
Nowadays, however, pastes are used less frequently and polishing with 2/1 stone would be quite OK.
There's process, when sharpener's angle is increased for final polish (2/1) and then slate is used with the same angle. People believe, cutting edge becomes stronger in this case.
Preparation before the first use
Stones with grits finer 3 microns either require preparation (dressing) with Silicium Carbide powders (SiC), or they will be self-polished after sharpening of 30-50 knives. Then they will be of gold color and work well.
For dressing you need flat (glass or cast iron) plate and set of SiC powders. The table below shows 2 grits for dressing, but you may use 3 or more to increase productivity. SiC grits were selected from widely available on the market, but the general rule is: starting grit is twice higher than stone's grit, finishing grit - the same as stone's grit. For example for 0.5/0 stone these are F400, F800 and F1200.
Selection of SiC powders for dressing of sharpening stones
| Stone | Starting grit | Finishing grit |
| 500/400 μ = 35/40= D501 | F16 (1230 μ) | F24 (745 μ) |
| 400/315 μ = 40/45= D426 | F16 (1230 μ) | F46 (370 μ) |
| 315/250 μ = 50/60= D301 | F24 (745 μ) | F46 (370 μ) |
| 250/200 μ = 60/70= D251 | F24 (745 μ) | F60 (260 μ) |
| 200/160 μ = 70/80= D213 | F36 (525 μ) | F60 (260 μ) |
| 160/125 μ = 100/120= D151 | F46 (370 μ) | F80 (180 μ) |
| 125/100 μ = 120/140= D126 | F60 (260 μ) | F100 (129 μ) |
| 100/80 μ = 140/170= D107 | F60 (260 μ) | F120 (109 μ) |
| 80/63 μ = 170/200= D91 | F80 (180 μ) | F150 (82 μ) |
| 63/50 μ = 230/270= D64 | F100 (129 μ) | F180 (69 μ) |
| 50/40 μ = 270/325= D54 | F120 (109 μ) | F220 (58 μ) |
| 40/28 μ = 550= M40 | F150 (82 μ) | F240 (46 μ) |
| 28/20 μ = 650= M25 | F180 (69 μ) | F320 (30 μ) |
| 20/14 μ = 1100= M20 | F240 (46 μ) | F400 (18 μ) |
| 14/10 μ = 1500= M16 | F320 (30 μ) | F400 (18 μ) |
| 10/7 μ = 1700= M10 | F400 (18 μ) | F600 (10 μ) |
| 7/5 μ = 3000= M6.3 | F600 (10 μ) | F800 (6,7 μ) |
| 5/3 μ = 4000= M4 | F600 (10 μ) | F800 (6,7 μ) |
| 3/2 μ = 6000= M1.5 | F800 (6,7 μ) | F1200 (3 μ) |
| 2/1 μ = 10000 | F800 (6,7 μ) | F1200 (3 μ) |
| 1/0 μ | F800 (6,7 μ) | F1200 (3 μ) |
| 0.5/0 μ | F800 (6,7 μ) | F1200 (3 μ) |
Also use method with CBN pastes on 3 iron plates. One iron plate for each grit size set (60/40 and 28/20, 14/10 and 7/5, 3/2 and 1/0), total working time 1 hour. This method is more expensive, but more effective.
If you have no previous experience with preparation, better leave this job to professionals. We stopped preparing stones because of war.
How to attach stone to blank.
Metal bond stone may be used without blank, but if you need more rigid surface or to maintain the same thickness of stones in the set (which is very convenient), attach to stone aluminum blank:
- attach marked area to blank (marked area is "damaged" with letters);
- use double sided tape, so you can easily remove and service stone with time if needed.
- if there's no such tape on sale (70 mm width), attach tape 25 mm width three times;
- attach tape to stone first, then to blank.
Use and cleaning
Use any comfortable oil (baby, olive..) to prevent glazing. And your sharpening stone would not glaze.
But if it glazed - clean with alcohol and toothbrush.
Maintenance is only needed every year or two, when you may need to flatten stone.
Resin and combined bond stones may be flattened with SiC powders.
Metal bond stones may be flattened also with FeCl (Ferric chloride), although SiC is OK too:
- 20 mins setting in 25% mixture (25 gr FeCl per 75 gr of water),
- few minutes polish movements (carefully draw "8") on glass plate.
That's all, you do not need special chemicals, tools, or equipment, see the video.
If you made a mistake and used FeCl for resin or combined bond stone, wash it well to stop reaction. Color of stone may change, but it will work good anyway.
Presentation of CBN sharpening stones, combined bond and how to prepare them for the first use.
Knife sharpening with CBN combined bond stones
Sharpening with Poltava diamond and CBN stones
Final polishing with Italian black slate