Knife Sharpening: How to Get a Razor Sharp Edge on an Old Knife

March 15th, 2017:

Recently, I found an old pocket knife that had been given to me years ago burried in my closet. The blade was in rough shape due to being poorly sharpened in the past. Today is the day I bring it back to life. Follow me as I walk you through the steps that will put a razor sharp edge on a knife that wouldn't win a fight against a stick of butter.

Step 1: Fixturing the knife for consistency.

There are many people out there who can sharpen a knife free-hand and achieve a beautiful edge. I am not one of them. Consistency is the key to any sharp blade, so I take the guess work out by using a clamping knife sharpener that can sharpent to the exact angle with ever stroke and every stone.

Secure the knife in the clamp on the spine. Make sure that the knife is clamped well so that it does not shift during sharpening.

 

Step 2: Choose the right blade angle.

The blade angle, or how narrow the knife edge is, has a large impact on how the knife performs. Shallow angles provide sharper edges, but less durability. Steeper angles provide more durability, but sacrifice sharpness.

Determine the sharpening angle to be used. For general sharpening and touch-ups, you will want to match the angle that the knife is already ground to.

This knife of mine had been used and abused for a long time. The edge was very rounded and gouged. Therefore, I decided to go with a 25 degree blade angle to achieve a balance between sharpness and durability.

 

Blade Angle Quick Reference

Blade Angle      Common Application
17 degrees      Filet knives, razor blades
20 degrees      Kitchen knives, higher-end pocket knives
25 degrees      Utility knives, hunting knives, most pocket knives
30 degrees      Axes, meat cleavers
 

Step 3: Begin sharpening.

Begin sharpening with the coarsest stone. Place a few drops of oil on the stone, set the stone at the correct angle, and place the stone on the blade. Begin sharpening with light pressure in a sawing motion, working up and down the blade. Try to use long, smooth strokes.

Once you see that you have an even grind on the entire edge of the blade, switch over to the other side and repeat.

A bur should begin to form on the edge of the blade as you sharpen it. This is a good indicator that you're taking off material all the way to the edge of the blade.

80 grit.

 

Step 4: Progress to finer grits.

 When you have achieved a smooth grind on both sides and a healthy bur has formed, step down to the next stone. Repeat the sharpening of both sides.

You can use a black marker to make sure that you've taken off enough material at each grit. Coat the edge of the blade with marker and make a single pass with the stone. If the marker remains anywhere on the edge, continue sharpening. Once a single pass evenly removes all of the marker, progress on to the next stone.

120 grit.

280 grit.

600 grit.

 

Step 5: Begin finishing.

Once you have sharpened your knife using each progressively finer stone, finish with a very fine stone (1000 grit or finer). This will create a polished finish that will resist wear and rust as well as provide a smoother cut.

1000 grit.

 

Step 6: Polish your knife.

Now that the edge is sharp, take a little extra time to polish up the blade and other components by using a polishing wheel. This has no impact on the quality of the cut, but goes a long way in making the knife more enjoyable to look at and use.

Before:
After:
 

-Drew Zdeblick, Mechanical Engineer

Posted in: DIY