The answer to this question depends on many factors. Some people take hours to sharpen a single knife on a Wicked Edge, while others sharpen knives in just a few minutes each.

These are the key factors: 

• Do you plan to reprofile the edge (change the angle)? Or do you plan to measure the current edge angle and then simply sharpen using that angle? 
• What level of finish do you desire? Are you trying to achieve a perfect, mirror-like polish on the edge, or are you simply trying to make the knife sharp? 
• What kind of steel is the knife made from? 
• Does the knife have any damage (like a chip or slightly broken tip) that you'll need to repair? 

When you first start using a Wicked Edge sharpener, it's important to develop a super solid understanding of the fundamentals, meaning you become comfortable with finding the knife's sharpening angle and determining the correct way to clamp the knife in the sharpener. You should also practice sharpening a lot to develop the muscle memory needed to comfortably and fluidly glide the sharpening stones against the knife's edge. Fortunately, all Wicked Edge sharpeners are designed to make things easy and hold the sharpening angle perfectly, so it's hard to develop poor techniques. Practice makes perfect. 

Once you have the fundamentals down, you can sharpen a knife in about 5-10 minutes. So, why does it take some people hours? Because they're aiming for aesthetic perfection and maximum sharpness. 

Reprofiling

To achieve maximum sharpness, the knife needs to be sharpened at a very acute sharpening angle (in the 15-degree range, or less), but not all knives are built with a 15-degree factory edge grind. This means you'll likely need to reprofile the knife to achieve maximum sharpness, which means removing a lot of material from the blade. If the factory grind on the knife is at 25 degrees, and you choose to reprofile to 15 degrees, the amount of time it will take could be anywhere from 30 to 60 minutes, depending on the coarseness of the stone you're using, how much pressure you apply with the stones, and how hard the blade steel is.  

If the knife has any damage, like a broken tip, plan to add some more time to repair it before you begin reprofiling the knife. 

Refining and Polishing the Edge

The next step is to rebuild and refine the edge using a progression of various abrasives from coarse to very fine. To create a highly-polished edge, it could take upwards of 12 different abrasives, and anywhere from 50 to 200 strokes with each of them to remove all the scratches from the edge. Harder steels will require more strokes with each abrasive to adequately remove scratches, and softer steels require fewer strokes. If you're sharpening at a relaxed pace, each stroke takes about 1 second. 

Making Minor Tweaks and Adjustments 

Every Wicked Edge abrasive is very, very slightly different in thickness. This has to do with factors like the size of the diamond particles on each grit of diamond sharpening stone. Varying thickness means a microscopic deviation of the sharpening angle with each abrasive progression. So, to account for this and achieve perfection, you can measure the sharpening angle at each progression using a digital angle gauge and make a micro-adjustment to the sharpening angle each time you switch to a different abrasive. Making this adjustment could add up to a couple minutes for each abrasive changeover. If it's 2 minutes, and you're changing your abrasive 16 times, that's another 32 minutes in total. 

By the time you combine the time from reprofiling the knife, making hundreds of strokes with each of a dozen different abrasives, and making minor angle adjustments throughout the sharpening process, I can definitely understand how someone can spend an hour or two or three sharpening a single knife.

The Problems of Perfection 

Knives that are that awesomely refined and gruesomely sharp have one flaw: they lose a giant percentage of sharpness the first time the knife is actually used to cut something. The finer an edge becomes, the more delicate that edge will be. Extremely hard steels do a better job at preserving sharpness for super-refined edges, but they're not impervious to dulling. Not to mention, most knives that people use on a daily bases aren't going to be made from extremely high-quality steel anyway. So, what good would it do to spend 3 hours sharpening a single knife for a customer who's just going to use it to chop an eggplant and reduce the knife's sharpness by 30% with a single slice? That would be about 2 hours and 50 minutes of work evaporating with a single use - not very efficient, and definitely not cost effective. 

If that's true about the sharpness reduction, why even bother making a knife that sharp to begin with? It's because its cool, and its fun to push the edge of the envelope sometimes. When you make a knife that sharp, you can actually get a little adrenaline rush when you test the edge. It can be addicting.  

Flawlessly polished edges aren't very practical. They look great, so there is a high demand to create mirror-like edges on high end collector knives, but a polished edge really isn't that great for every-day use. When you polish an edge, the edge's apex will be very smooth (without micro-teeth). When using knives, you want the edge to have some micro-teeth, like a microscopic saw, so the knife actually bites into what its cutting. This is especially true if the knife will be used in a draw-cut (pulling) motion. The only time a very polished edge is effective is when it's being used for push cutting (think whittling wood) or shaving. 

Sharpening Knives in Under 10 Minutes Each

To sharpen knives in under 10 minutes, all you need to do is know how to focus your efforts. The reason it takes so long to reprofile knives to more acute sharpening angles is because you need to remove material from the shoulder of the edge in order for the stone to finally touch and be able to refine the edge's apex. So, to reduce your sharpening time, simply discover the current edge angle and then set your sharpener to sharpen at that angle so the stone hits the edge's apex right off the bat - don't reprofile the knife. If you are simply matching the current angle of the knife, the difference in time brought on by varying qualities of steel becomes a lot more minor of an issue. 

For practical use and most cutting applications, an edge with a 1000 grit finish is perfectly adequate. This means instead of progressing through 12 or more abrasives, you only need to use 6. When you're not concerned about the aesthetics of the edge you don't need to remove every single scratch, so you only need to do about 10-20 strokes with each stone to achieve sharpness.

And finally, the minor variations in sharpening angle brought on by various factors aren't enough to prevent a knife from getting sharp. Wicked Edge sharpeners are very precise machines. From my experience sharpening over 10,000 knives on a Wicked Edge, you don't need to worry about this if your goal is to make the knife sharp for practical use. 

Personally, I try to keep my sharpening time at about 5 minutes per knife. You can achieve 10 minutes per knife very easily, and your time will reduce to 5 minutes as you practice more and more. 

• Match the existing edge angle (no reprofiling, ever!)
• Use diamond stones in 100, 200, 400, 600, 800, and 1000 grit with 10-20 strokes with each stone on each side of the knife
• Try to prevent unwanted variables (like the knife moving while your sharpening) but don't obsess over tiny angle variations 

With the above philosophies put into practice, you can make a knife sharp enough to impress almost anyone. I like to think about sharpness like 100-meter sprinters. In the NCAA D1, good 100-meter times for men range between 10.13 and 10.90 seconds. The Olympic world record holder, Usain Bolt, ran the 100-meter dash in 9.63 seconds, which means he dedicated his whole life to achieve a time of less than 1 second faster than a good college time for that race. In a competition, that extra time, training, and dedication pays off. It's what separates good athletes from great athletes. But in practicality, I would still get my ass kicked in a 100-meter race by both the college athlete and Usain Bolt, and without a stopwatch I wouldn't have any clue that one was faster than the other. Sharpening knives in 10 minutes or less on a Wicked Edge sharpening system is like the college athlete, who still happens to be faster than 99.999998% of people in the world. The people using the Wicked Edge and taking 2 hours to craft their knives are aspiring to be the Olympic gold medalists of knife sharpening. 

Most people who hire sharpening services to sharpen their kitchen knives won't be able to appreciate the difference in the performance of their knives between a 2 hour sharpening job and a 10 minute sharpening job on a Wicked Edge, and my personal opinion is that it's not worth the extra hour and 50 minutes to sharpen a knife for a customer who wouldn't be able to recognize the difference, and who certainly wouldn't be willing to pay for that amount of labor. I'm not saying there aren't people out there who would be willing to pay for that level of service. In fact, there are probably many who would, but I think those customers are much harder to find and they're not who I market my sharpening service toward.

Personally, I try to keep my sharpening time below 5 minutes per knife. At that pace, I'm maximizing the amount of knives I can sharpen and revenue I can generate per hour, while still providing my customers with excellent results.