Knife Sharpeners, The World's Finest

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Professional Knife Sharpening

By master knife maker and expert sharpener Lyle Brunckhorst of Bronk's Knifeworks

                                                             

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A Guide to Professional Knife  Sharpening

"The Secret World of Sharpening"

 

Getting down to it.

Sharpening

OK, letís get started. The edge angle, or the angle that the blade is sharpened at, is dictated by what you plan to use the knife for. There is no set rule as to what angle you have to sharpen your knife, but a good guide line is sharpen most of your working knives at about 20 degrees on each side of the blade to give you about 40 degrees. This will give you a durable edge for most chores.

A very popular practice is to grind the blade at 15 degrees until you are nearly to the edge and then finish at about 19 degrees. This makes for a very keen and yet durable edge.

The straight razors were sharpened at a very thin angle and were made with the sharpening guide built into the design of the blade. In other words the back of the razor was forged thicker on the very spine of the blade so that the blade could be laid down flat on the sharpening stone with both the edge and the spine touching the stone. The spine held the edge at the proper angle to the stone for sharpening. Slick huh?

This feature is not incorporated into most knives, as the thicker spine would create a problem or obstacle with most slicing and cutting chores and the edge would be too fragile for most cutting tasks. A sharpening guide that temporarily clamps on the back of a knife works in the same way and does make a very good sharpening system. There are other systems used in holding the proper edge angle during sharpening and they are all very useful.

Some years ago I noticed Ben Dale at the knife show in Eugene, Oregon demonstrating his sharpeners. I didn't stop at first because I have seen my share of pitchmen hawking their doodad tools for sharpening knives and most make me shudder to see what they do to a knife. During a quite time at my booth, I started thinking about what I saw and it began to make sense so I went back for a better look. I have been sold on this system ever since and have sold a number of them to satisfied customers for several years. I personally find the Edge Pro system to be my favorite hand knife sharpener. Although it does cost a bit more than some sharpeners, it is easy to use, very accurate and built to last a lifetime.

The Edge Pro works very well on the vast majority of knives with ease. The fact that you do not have to clamp the blade at different locations and you can just move the blade along the shelf is very efficient. The drawback is that some knives do not have a flat blade and will rock back and forth, making it difficult to get a perfect edge angle. Usually this is solved by making sure that the ricaso (that flat part just ahead of the guard) is resting firmly on the shelf. Or you can put a narrow strip of tape on the shelf or blade to support the blade edge to prevent the rocking. On really small blades you may have to set the blade a little askew on the corner of the shelf so that the stone does not abrade the shelf. Again using the ricaso to hold things steady at the proper edge angle.

The Edge Pro sharpener, in my opinion, is one of the best knife sharpeners ever invented. It normally comes with a 180 grit stone and a 220 grit stone from the manufacturer. This system as it comes may be all you would ever need for your kitchen knives, however I like my knives sharper than that and if you can eliminate the burr that is developed with the first stone, the edge is more durable. One of the systems that I offer (Special) comes with a 220 grit stone, a 320 grit stone and also in addition a 800 grit stone for those of us who have to have that ultimate edge. The Edge-Pro will give you a whole new perspective on what sharp is.

 Most of us can train ourselves to hold an approximate but constant angle while stroking a stone but it does take some practice. I find that I am getting proficient enough at holding an accurate edge angle but I would rather get to an even greater edge with little effort?

Once you have chosen the best edge angle and start to work, you should see that you are now removing the metal just behind the projected edge. Do this on both sides and with a fairly course stone until the new facets just come together to meet at the very edge. The best way to tell when you have arrived at the edge is when you can no longer see the edge while looking straight down at it or you can see or feel a burr all along the edge. Unless you want it to be a special purpose knife such as a patch knife or sushi knife, sharpen evenly from both sides of the knife. If you do sharpen only one side, use a somewhat steeper edge angle in order to get the proper final edge angle as with a conventional blade.

Most of the work will be done with the course stone, one that moves steel quickly. Once you have obtained a burr all along the entire edge with say a  120    or 220 grit stone, change to a finer 320 grit and using the same angle polish out the course marks left by the first stone. The succeeding finer grits will require very little work and will need very little pressure. If you desire a shaving type edge, change to 800 grit and repeat the process. The wire edge burr will get very thin with succeeding grits and will buff or strop off easily. I should mention that a polished edge will be both sharper and more durable, because you have a real edge instead of a thin wire burr that requires a steel to straighten out as it folds back over the blade edge.

Sometimes it works better if the last grit is set just a smidgen steeper with the last couple of strokes so as to work on the edge only.

For a closer look at how an edge will appear after using various size of grits read the article written by Dr. John Verhoeven.

Many professionals prefer a double angle edge where the primary grinding is done at a very narrow angle to thin the blade and the very edge is lightly touched with the steeper more durable angle. This configuration coupled with proper blade geometry produces a very good working knife that has reduced drag and an easy to maintain edge between major sharpening.

For the power tool minded, there are a wide variety of belt grinders and buffers. I have sharpened thousands of knives over the past 31 years using this method. You really have to pay strict attention to heat build up, as it is very easy to get the blade hot and ruin the temper. There are other power tools designed for sharpening and the ones that run slow and wet are among the best. The automatic knife sharpeners that you insert the blade and pull through make me shudder, as they remove an excessive amount of steel and never do get the blade sharp and can grind out deep scallops in the knife. It reminds me a little of a kid with a pencil sharpener, soon you have nothing but short pencils.

Heat is your enemy here and needs careful watching. If you are grinding up on the thicker part of the blade, as if in reducing the over all blade thickness, heat build up is not so pronounced, because the heat has several directions to flow and there is mass under the contact area for the heat to flow to. When you are grinding at the edge of the blade there is very little mass to absorb the energy and only half as many directions for heat flow. Grinding at the tip of the blade has to be done with extreme care as the heat has no place to go.

Belt grinders will produce a much better finish than a hard wheel grinder, especially if you use the slack part of the belt because it blends better. You can get a variety of grits from course to fine. The most popular size for knife makers is the 2Ē times 72Ē belts and they come in grits from 36 to 2,000 and no grit for rouge.

Use the slack part between the contact and tracking wheels. I highly recommend that you let the belt run away from the edge, as shown in the illustration, not into the edge. (install a motor reversing switch on your belt grinder just for this job). I can hold the blade somewhat horizontal with the motor in reverse and watch the burr pop up along the edge as I grind in the bevels. Donít place the blade edge into the running belt as is done with the bench stone. If you do, you may actually cut into the belt and bad things will happen at light speed. I have a big scar on my left thumb for testimony.

  

If your belt runs vertical as in most two wheel grinders, hold the edge down and let the belt run off of the blade.

Determining the right angle to hold the knife to the belt or stone can be done by actually setting the angle with a protractor, until you get a feel for it. First set the blade edge on something flat and using a protractor or other devise raise the back to 20 degrees or any other angle you want.

 

While the blade is at this angle gauge the distance of back of blade to the flat surface and visually remember this distance.  Another useful trick that I use at times is to paint the edge with a magic marker. You can tell at a glance just exactly where it is that you are honing on the edge.

A quick angle to use is to divide a right angle twice. 90/2 = 45, 45/2 = 22.5 for a really durable using edge, however I like a sharper hunting knife so I would drop the blade down a few degrees from that.

Now all you have to do is remember the proper distance to keep the back of the blade from the stone or the grinding belt. Take even passes from heal to point, alternating from one side to the other, until you get a burr all the way along the edge from both sides. A lot of blades will have a varying thickness along the edge and this will mean more work in some areas, and maintain the same angle throughout. Do not change grits until you have a burr formed from heal to point. Now you can change belts or stone and repeat the process but take very light passes. Start with a 120 grit belt unless the knife is really bad and follow up with a 400 grit belt and finish with a worn out belt that has been lubricated and rouged.

The same procedure goes for sharpening by hand. Start with a course enough stone to remove the metal quickly and follow up with the finer stones. Sharpening a dull knife, from the start, with an Arkansas hard stone is akin to digging a basement with a teaspoon or felling a giant redwood with a pocket knife.

Buffing the final edge is widely practiced and does a very quick and efficient job of removing the final burr and bringing up the edge. It needs to be done with care as well so that you do not build up heat and remove the temper. The buffing wheel will conform to the shape of the blade however and can run across the edge of the blade at an angle much steeper than what you initially ground it to and ruin your efforts. To prevent the buffer from destroying the edge, reduce the angle just a little that you hold the blade to the buffing wheel but not so low as to let the buffer catch the top of the blade either.  Sometimes even I will lose the edge from over buffing and will have to start from scratch. Buffing take a little practice but the results are well worth the time spent learning. Buffing is also the most hazardous work in the knife shop. A blade that is not presented to the buffer properly can be caught by the buffer and thrown with great force.

 

Things to remember when using the buffer. Keep the blade below the center of the buffer shaft so that if it is caught it will not be thrown directly at you. Keep the edge down and donít let the buffer drift up to the top edge of the blade and keep the point of the blade down also. If your buffer catches the edge or the point of the knife it will get a much better grip on the blade and may destroy the buffer pad to boot.

There are some more good rules to remember.

Use a sewn buff, not a loose buff and if you think you just have to buff a double edge blade check your insurance policy first. Last but not necessarily least, slow your buffer down. Do not use a 3600-rpm motor with a large wheel unless you really like to live on the edge so reduce the speed down by belt and pulley. The larger the buffing wheels the faster the surface travels at a given rpm, so donít get carried away with size. Get one large enough to clear obstacles like the motor, pulleys or whatever and run it slow (1750 rpm). If you have a faster motor, use a smaller buffing wheel and extend it with an adapter if necessary to clear the motor.

 

Scary Sharp the Sand Paper Way.
 
Over the years I've found that the flat glass and auto body wet and dry sanding paper works as well as anything for some sharpening jobs such as chisels or planes.

The job starts at the grinder by hollow grinding the bevel nearly to the edge being careful not to over heat the blade and keeping the grind straight and even.

Starting with a course grit of silicon carbide paper that is flat to the glass, set the blade edge and heel on the paper and drag it along the paper until a burr forms along the cutting edge.

Change to a finer grit and lay the chisel flat on the back and drag until the burr has straightened out. Now place the edge and heel to the same paper and hone again by dragging the edge over the paper at an angle that will produce a scratch pattern at an angle different to the original angel. Proceed until the first scratches are gone.

Repeat this process until you have gone from the coarsest paper of about 120 grit all the way through 2000 grit. The first grit will take the most time and the finer grits will require very little pressure or time to remove the previous scratches.

As you go from grit to grit, the burr will get finer until at last it will fall of as you go back and forth from one side to the other with the last 2000 grit.

For a more in depth, detailed, long winded and tongue in cheek account of this style of sharpening go to http://www.shavings.net/SCARY.HTM#original

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Last modified: 08/31/08