Electric sharpeners use rotating ceramic or abrasive-impregnated metal wheels to grind a new edge into a blade. Low-end models, which start at about $25, feature a single set of coarse wheels that produce a rough, if potentially serviceable, edge—it depends on how even the edge is, and that’s a matter of overall design and engineering. Higher-end models can cost $200 or more (and professional models for slaughterhouses can approach $1,000), but they feature stronger motors and multiple grinding wheels—coarse, fine, and often polishing/honing—that when well-engineered can put an extremely keen, durable edge on knives of every style and quality.
The toughest angle to master is the angle at which you'll sharpen the edge of the knife. For a Japanese knife, that should be around 12-15 degrees. Before you reach for the protractor, a good test is to get roughly half an index finger's gap between the spine of the knife and the stone (see above). Remember to remove your finger before you start sharpening. For a Western-style knife, you want an angle of about 20°, so raise it ever-so-slightly higher.
TO USE: Soak stone in water for no more than 5-10 minutes. Place stone on a damp cloth with the courser 400 grit side (dark green) facing up. Hold the knife so that it’s flat and perpendicular to the block, with the blade facing left. Holding the knife at a 20-degree angle, slowly sweep the edge of the blade from left to right down the length of the stone and continue until sharp. If stone starts to feel too dry, add more water. Be patient and take your time. Flip knife over and repeat on the other side (now moving from right to left). Be sure to sharpen both sides evenly. To polish the blade further, flip stone over to the fine 1000 grit side (light green) and repeat the process. When blade is honed to desired sharpness, wash and dry your knife. To clean your stone, simply rinse with water, wipe away any remaining metal residue with a rag, rinse again, then dry.

As opposed to water whetstones that require you to pre-soak the stone, the Norton oil stone is pre-filled with oil to save time and eliminate the need to pre-soak it prior to use and the lubricant stays on the surface during sharpening.  The oil also prevents metal from bonding with the abrasive surface by flushing away dislodged abrasive and metal chips.
People often describe the Trizor XV as putting a 15-degree edge on a blade, but the reality is a bit more complex. It in fact produces what Chef’sChoice calls a Gothic Arch Edge, which consists of three distinct bevels, the final one at 15 degrees. Not surprisingly, the company claims that this “blade architecture” is more durable than a single bevel. More convincingly, the testers at Cook’s Illustrated and America’s Test Kitchen use the Trizor XV on all their knives and actually convert 20-degree knives to the Gothic Arch Edge. (Europe’s medieval cathedrals, too, attest to the strength and durability of the Gothic-arch form.)
This coarse grit whetstone is great for prepping old and dull knives that need to be sharpened with a fine grit stone. One of my good knives edge looked like someone had tried to chop barbed wire. After ten minutes on each side of the stone, the edge was smooth and free of imperfections. After it hit the knife with the fine grit stone, I was cutting onions and apples like hot butter! I would soak this stone for 12-24 hours before using. It sucks water like a sponge. The surface needs to be damp when you sharpen.
The basic concept of sharpening is simple – you're using an abrasive edge to remove metal – but the knife you buy may alter the method you should use. A general rule of thumb is that a waterstone can be used for both Japanese- and Western-style blades, but you should avoid pull-through sharpeners for Japanese knives (or any knife with very brittle blades).

This pocket-sized tool sharpens knives using carbide sharpening blades, then gives the knife a smooth finish using ceramic blades. A diamond rod is used for honing knives or for sharpening serrated knives. This is a great tool to keep in the toolkit, the tackle box, or to carry along when camping. Since it’s small, your hands will be close to your sharp knife blades as you work, so you might want to save it for occasional use rather than for sharpening all of your kitchen knives on a regular basis.

I'm a novice knife sharpener. I've had to unlearn what my grandpa taught me in order to use these. So far, I've had decent but mixed results. I've switched to my cheap 200/400-ish cheap tool stone from harbor freight for cutting a bevel when the blade has either been damaged or did not have a proper bevel. The 400/1000 grit stone in this kit is soft. Very soft. I have bowled it out several times. It makes keeping a steady angle difficult. But these stones at this price point are meant for learning, and for that they serve their purpose.
One of the only things we don’t like about the Idahone is the lack of a prominent finger guard where the rod meets the handle. As a result, we highly recommend using the safer “supported” technique for honing a knife, as demonstrated in our guide to chef’s knives. In this method, the rod is held against the counter or cutting board, and blade always moves away from your body and grip-hand, greatly reducing the chance of a nasty accident.

The composition of the stone affects the sharpness of the blade (a finer grain, usually, though not always, produces sharper blades), as does the composition of the blade (some metals take and keep an edge better than others). For example, Western kitchen knives are usually made of softer steel and take an edge angle of 20–22°, while East Asian kitchen knives are traditionally of harder steel and take an edge angle of 15–18°. The Western-style kitchen knives are generally in the range of 52–58 on the Rockwell scale, which denotes the relative hardness of a material.
Historically, there are three broad grades of Japanese sharpening stones: the ara-to, or "rough stone", the naka-to or "middle/medium stone" and the shiage-to or "finishing stone". There is a fourth type of stone, the nagura, which is not used directly. Rather, it is used to form a cutting slurry on the shiage-to, which is often too hard to create the necessary slurry. Converting these names to absolute grit size is difficult as the classes are broad and natural stones have no inherent "grit number". As an indication, ara-to is probably (using a non-Japanese system of grading grit size) 500–1000 grit. The naka-to is probably 3000–5000 grit and the shiage-to is likely 7000–10000 grit. Current synthetic grit values range from extremely coarse, such as 120 grit, through extremely fine, such as 30,000 grit (less than half a micrometer abrasive particle size).[citation needed]
One problem the edge pro suffers from is different thickness stones. When going from one stone to another, the variance can change the angle and create either a lot more work or an inconsistent edge. One way to solve the problem is by installing a 5/16" drill stop collar. A simple Google search for "edge pro 5/16" stop collar" should yield a video to explain the simple install.

Before you start sharpening, soak the stone in water for around five to 10 minutes, until it absorbs the water and a liquid film appears on the surface. After soaking, splash some water on top, and re-splash during the process if it ever gets too dry. You'll get a dark, splotch of steel and stone building up on the stone while you're sharpening the blade. This is totally normal so just splash the stone with some water to clean it off and allow it to perform more efficiently. 
I like the fact that there are two different grits (can be seen as two colors). the black rubber feet stick to the kitchen granite top like glue. The 1000 does a pretty good job of getting a knife roughly there and the 4000 puts on a fine polish for razor a sharp edge. I would go the extra step of stropping the knife after the grinding operation for an extra sharp edge.

After 15 hours of research and testing, and several adult lifetimes of kitchen experience, we recommend the manual Chef’sChoice ProntoPro 4643 as the best mechanical knife sharpener. It’s impressively simple—almost intuitive—to use: You run the blade back and forth between its diamond-impregnated sharpening wheels to cut and then hone a new edge. The ProntoPro 4643 works on both traditional European and Japanese knives, which use different edge angles, making it universally utilitarian. (Note that we also link to otherwise equivalent but cheaper single-angle sharpeners below.)

Modern synthetic stones are generally of equal quality to natural stones, and are often considered superior in sharpening performance due to consistency of particle size and control over the properties of the stones. For example, the proportional content of abrasive particles as opposed to base or "binder" materials can be controlled to make the stone cut faster or slower, as desired.[7] Natural stones are often prized for their natural beauty as stones and their rarity, adding value as collectors' items. Furthermore, each natural stone is different, and there are rare natural stones that contain abrasive particles in grit sizes finer than are currently available in artificial stones.[citation needed]
As the video of our test shows, the Trizor XV took a very dull, very heavy (and slightly bent) 12-inch Wüsthof chef’s knife and made it tomato-slicing sharp. Setting the new edge took about 20 strokes on the coarse wheel; the fine and polishing steps took about 10 and five strokes respectively. All told, the process was perhaps three minutes of work. The motor was impressively powerful, never allowing the sharpening wheels to bog down or “catch” in the metal of the knife. It sharpened blades to within about ⅜ inch of the heel—as with the manual ProntoPro 4643, excellent performance, and a testament to the attention that Chef’sChoice pays to overall design throughout its extensive product range. This sharpening of virtually the entire blade is important. Without it, not only do you lose the ability to cut with the heel of the knife—especially useful when you’re cutting tough root vegetables, where employing the heel provides stability and pressure—but also over time the blade edge develops a “dish,” or dip, that prevents the rear portion of the blade from contacting the cutting board and slicing all the way through a food item.
A diamond plate is a steel plate, sometimes mounted on a plastic or resin base, coated with diamond grit, an abrasive that will grind metal. When they are mounted they are sometimes known as diamond stones.[12] The plate may have a series of holes cut in it that capture the swarf cast off as grinding takes place, and cuts costs by reducing the amount of abrasive surface area on each plate. Diamond plates can serve many purposes including sharpening steel tools, and for maintaining the flatness of man-made waterstones, which can become grooved or hollowed in use. Truing (flattening a stone whose shape has been changed as it wears away) is widely considered essential to the sharpening process but some hand sharpening techniques utilise the high points of a non-true stone. As the only part of a diamond plate to wear away is a very thin coating of grit and adhesive, and in a good diamond plate this wear is minimal due to diamond's hardness, a diamond plate retains its flatness. Rubbing the diamond plate on a whetstone to true (flatten) the whetstone is a modern alternative to more traditional truing methods.[13]
A hybrid manual-electric sharpener, the Chef’sChoice Hybrid 210 uses a motor and abrasive wheels to grind the new edge and employs a manual stage to hone it. This sharpener is eminently affordable. However, our top pick, the ProntoPro 4643 multi-blade-angle manual model (as well as its $30 to $40 single-blade-angle kin) produces a better edge and doesn’t make us worry about breakdowns the way the Hybrid 210’s lightweight motor does.
I really like this stone. The 1000/4000 grit combination is perfect for my needs. I'm a woodturner, and belong to a club that brings in professional turners from around the world. One had an eye opening test of sharpness. He stacked around 25 new razor blades in a box with one open side. The box assured that the blades were in perfect alignment. If you looked at the blades' sharp ends head on, all you saw was black. His point was that if you can see the edge, the blade is not sharp. Any reflection from the edge, again, facing it head on, is a dull spot. My long story leads to the fact that I was able to sharpen several knives to the point of not seeing the edge. This is not the stone to use if you are trying to remove nicks from a blade. A lower grit will do that job. This is for putting a fine, "invisible" edge on the blade, and with the right technique, that's what it will do. Another thing to consider is the fact that these stones are "sacrificial" A stone wears because it is deliberately giving up dull surface particles to expose the sharp ones below them. Anyone expecting a stone to last forever is mistaken. Bottom line? I think this is a great stone that takes my knives to the level of sharpness I need in both woodworking and cooking. I also like the rubber frame it sits in, giving you much better control over the stone. Your efforts can go into sharpening without having to steady the stone on your workbench or countertop.