Speed for Electric Knife Sharpeners

This test is part of How We Test and Rate Electric Knife Sharpeners v1.0

We all want a sharpener that’s quick to bring an edge to our knives, but especially so when it comes to electric machines.

Electric sharpeners are supposed to give your knife a super sharp edge in a hurry. The sharpness is expected to resemble what a whetstone can produce, but take far less effort. The speed at which a machine brings a dull knife to high-grade sharpness is thus a critical factor when considering which to purchase.

How We Determine the Speed 

An electric sharpener’s speed is determined by the total time it takes—including setup time—to bring a dull knife to sharpness level 9.

Level 9 is the highest level of sharpness in the Practical Sharpness Scale. To qualify for this level, the knife must be able to cut through a string of raw beef tendon with minimal force applied by the operator. Our experience suggests that all electric sharpeners can achieve this benchmark, though the time it takes varies from one device to another.

Equipment

Here’s a list of what we use to conduct the test.

• Electric sharpener
• 8-inch, 20-degree-bevel, stainless steel chef’s knife 
• Sandpaper for blunting the knife
• Printing paper for pre-testing sharpness
• Raw beef tendon
• Cutting board
• Clock app to record the time

To reduce the number of variables in our test, all the test knives are identical at the outset. We use a fresh piece of sandpaper of the same brand and grit to blunt each knife. It’s a little more challenging to find identical beef tendon strings, but we try our best to keep the type and size consistent.

The Test Procedure

Here are the steps we take for this test.

1. Resetting the Edge

We sharpen to edge angles between 15 and 22 degrees, depending on what the electric sharpener offers. With devices that sharpen at more than one edge angle, we choose the value closest to 17.5 degrees.

All of our test knives start out with a 20-degree edge angle, so we have to reset the edge to each device’s pre-set angle before testing. This is because the ‘breaking in’ task—the first time you sharpen a knife using a different angle—doesn’t represent the sharpening process that happens later on a regular basis.

To do this, we run the test knife through the sharpener following the user’s guide until the edge settles into its new, permanent shape and angle.

2. Blunting the Edge

We run the knife across sandpaper for 60 seconds to destroy the edge.

3. Sharpening

We run the knife four times through the coarsest set of slots (which translates to eight strokes in total), then inspect the edge for sharpness. We test the knife on printing paper and if it appears sharp enough, we test it on beef tendon. 

If the knife needs a lot of force to cut through the beef tendon, it’s brought back for another four pairs of strokes until it needs very minimal force.

We then move on to the next stages of sharpening with three pairs of strokes on each stage, and test the knife again on the beef tendon.

We record the whole testing process and write down the total time and number of strokes used as well as the pressure we had to apply while cutting.

How We Rate Speed

If you regularly sharpen and maintain your knives, 2 - 4 minutes on an electric sharpener will usually be enough to restore its edge. However, since many people use electric sharpeners for serious, deep sharpening, we deliberately blunt the test knives to an unusable degree and sharpen them back to the highest sharpness level. As such, our process takes a bit longer than yours probably would. 

Ideally, machines that do the job in only 2 minutes are granted 10 points, with each additional 30 seconds translating into a deduction of 0.5 points. Those that take more than 10 minutes are granted only 1 point.

A very light cutting feel is worth a 0.5-point bonus while a heavy feel results in a 0.5-point deduction.