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Tool Sharpening 101: Stones

Different types of sharpening stones exist for a reason – there is not one type or style of stone that is best for every sharpening task. Choosing the one that best one is a matter of matching the best combination of advantages for your particular sharpening needs.

sharpening stones: four types.The three most common types of sharpening stones are oil stones, water stones, and diamond stones. There are also ceramic stones which are more commonly used for knife sharpening. Each of these stones has its own advantages that can help users achieve their sharpening goals.

Oil stones are the sharpening stones that we most commonly associate with tool blade sharpening because it is what many of us grew up using. The stones are made from Novaculite, Aluminum Oxide, or Silicon Carbide. Oil is used to remove the filings of stone or metal produced during use.

Natural Stones, known simply as Arkansas Stones are made from Novaculite and accounts for most of these stones. They are quarried in Arkansas, hence the name. Stones stones are divided into grades relative to density and the finish the stone produces on a tool's edge. The four finer grades are Soft Arkansas, Hard Arkansas, Hard Black Arkansas and Hard Translucent Arkansas. These stones are capable of producing a polished edge, but cut more slowly than man-made stones.

The Aluminum Oxide oil stones are man made. These stones can cut fast and can also produce a fine edge on tools and knives. The grading system for these stones are fine, medium, and coarse. Compared to the natural Arkansas stones, these stones are more coarse however. Also known as 'India Stones' they are often used as a companion to an Arkansas Stone so that all degrees of courseness are covered.

Stones are made of Silicon Carbide and the fastest cutting of all the oil stones. They are graded as fine, medium, and coarse. These stones are not used to produce an edge – they are best used for initial coarse sharpening. To achieve a well-honed edge, in the shortest time, it is common practice to start with a Coarse Silicon Carbide stone move on to an India Stone and then follow-up up with an Arkansas Stone.

Water Stones have a large following due to their many advantages. Like the oil stones, the water stones are available in both natural and synthetic materials.

Synthetic water stones are generally made of Aluminum Oxide. This is the same abrasive material used in the India stones. The difference is how the binders that create the stone. Synthetic water stones are softer than India stones, which means a faster cutting action. That fast cutting is an advantage of the water stone. The other obvious advantage is the use of water rather instead of oil to remove filings and degris from the stone. Unfortunately, the softness that provides a fast cutting medium also wears the stone down more quickly. That softness also promotes uneven wear which means the stone had to be periodially flattened to bring it back into shape.

Diamond Stones are actually metal plates which are embedded with small industrial diamonds. There are two main types of diamond stones. The more common style contains holes in the diamond surface to capture filings. These stones cut very fast and are simple to use. The other type has a continuous diamond surface – no holes for the filings to collect. This is the preferred stone for tools with points that could become damaged by using the first type.

The key advantages of a diamond stone are the fast sharpening and the flatness of the stone. In fact, extra-coarse diamond stones are the preferred tool to flatten oil or water stones. The biggest disadvantage of the diamond stone is cost.

Ceramic stones were the early replacement for natural stones. There is a huge disparity in quality and hardness of ceramic stones. Some are extremely soft and constantly require flattening and some are so hard they glaze over. Ceramic stones use water to flush the filings from the surface and require a lengthy soaking period of 10 minutes or more prior to use.

Oil Stones
Advantages   Disadvantages
1. No slurry required
2. Relatively inexpensive
3. Does not cause rust
4. Available in a variety of sizes & grits
  1. Oil can cross contaminate wood
2. Coarse stones wear quickly
3. Requires flattening
Water Stones
Advantages   Disadvantages
1. Quick aggressive cut
2. Wide range of grits
3. Fine grits offer superior finishing & polishing
  1. Wear quickly
2. Must be flattened often
3. Can be damaged by tool edge
4. Requires a slurry to use
5. Water can cause rust
Diamond Stones
Advantages   Disadvantages
1. Cuts very fast
2. Very durable & wear resistant
3. Stays flat and used to flatten other stones
4. Can be used without lubricant
  1. Must adjust sharpening methods (light strokes)
2. No polishing grits
Ceramic Stones
Advantages   Disadvantages
1. Do not require flattening as often as other stones
2. Available in very fine grits
3. Very wear resistant
  1. Very fragile
2. Will clog without lubricant
3. Wide range in quality and hardness



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