A number of firms manufacture Synthetic Waterstones. Generally speaking, Synthetic Waterstones can be classified in the same three groups as natural stones, with the exception of the Super Finish stones:
- Very Coarse Stones, for the maximum removal of metal, are available in #80 to #400 grits.
- Medium Coarse Stones, for refining the edge and establishing the “burr,” are available in #700 to #2000 grits.
- Finish Stones, for final honing and polishing of the edge, are available in #3000 to #6000 grits.
- Super Finish or Polishing Stones are available up to a #30,000-grit stone.
In addition to different grit sizes, stones come in a variety of abrasive materials, as well as from different manufacturers. Generally, the more expensive the stone, the faster it will cut per grit size and the longer it will last.
A typical sharpening sequence is to first establish a flat bevel and remove any nicks with one of the Very Coarse or Medium Coarse Stones. The choice of grit depends basically upon how much material needs to be removed from the bevel in order to leave a clean, true edge. If there are no nicks or other defects, the #1200- or perhaps #2000-grit stone is the best choice. However, if more metal needs to be removed, the #700-, #800- or #1000-grit stones cut faster. This, of course, means less effort will be required.
The #80- through #400-grit stones are the best choice when a considerable amount of metal must be removed. Keep in mind, though, that these stones will leave scratches, which must be removed with a Medium Coarse Stone prior to final polishing.
After the medium coarse sharpening is completed and a “burr” is obtained, the tool is transferred to a Finish Stone and alternately honed on back and bevel sides until the “burr” is totally removed. Finishing or polishing can be accomplished in one step, with any stone from #3000 to #8000 grit. However, in general, a better edge will be obtained if the tool is first honed on a #3000- or #4000-grit stone prior to final polishing on #6000- or higher-grit stone.
Preparing Stones for Use
Some stones require soaking prior to use, while some do not, so it is best to follow the manufacturer’s recommendations for preparing the stone for use. If the stone does require soaking, it is best to fully immerse the stone in water. The stone is ready for use when bubbles cease rising to the surface. It is recommended to have a water-filled spray bottle on hand to keep your stone wet during the sharpening process, regardless of the type of stone being used. Under no circumstances should any oil-based lubricant be used, as this will ruin the stone.
Flattening Your Stone
It is very important when sharpening chisels and plane irons that your stones be flat. Checking for flatness is particularly important, since any irregularity in the surface of the stone will be transferred to the tool’s edge. After a bit of experience, you will be able to tell by visual inspection whether or not a stone is flat. You may use a straightedge for this purpose or simply flatten the stone prior to each use.
The easiest method to flatten a Coarse Stone is to rub it across wet/dry sandpaper placed on a flat surface. If your stone is fairly flat, #220-grit sandpaper is sufficient. If a greater amount of material needs to be removed, then coarser sandpaper such as #120 grit is appropriate. A Finish Stone is easily flattened by rubbing it together with a previously flattened Coarse Stone.
How to Sharpen
Now that your stones are flat and wet, you’re ready to begin sharpening. Place a Coarse Stone on a flat, secure surface so that it will not shift during use. Begin rubbing the tool back and forth on the stone. Allow the “mud” to build up and remain on the surface. This will give a better sharpening effect and ultimately, a keener edge. Should the stone’s surface begin to dry out during sharpening, add a fingertip or two of water to the surface, or spritz the surface with your water bottle. As soon as a wire edge or “burr” is obtained, transfer to a Finish Stone and complete honing the bevel and back side of the blade. Proceed on the Finish Stone as already described for the Coarse Stone. If the tool requires a considerable amount of sharpening, periodically check to ensure that the stone’s surface is flat. If not, flatten the stone as previously described.
Nagura Stones
Some Finishing Stones require the use of a Nagura Stone to produce “mud” or paste on the stone’s surface during honing. There is some controversy over what the Nagura actually does in the sharpening process but it does make the stone surface of some of these very fine stones slipperier thus helping to keep the tool from sticking ensuring a smooth sharpening action. A Nagura Stone is easy to use. Simply rub it in a circular motion on the full surface of a Finish Stone until a paste develops. If the stone surface is too dry the Nagura Stone will stick. To alleviate this problem, add a few drops of water. Generally speaking, the more paste, the better the honing action. Not all waterstones require a Nagura stone to work properly, so it is recommended that you follow the manufacturer’s directions.
