Sharpening: The Age Old War!

K

KnifeChick

Joined
Oct 31, 2000
Messages
16
So Many Options, so few really sharp knives!
What do you guys seem to think is the best way to get a good edge on 420-440 stainless blades?
To Leave a Burr or not to Burr..that is the question!
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Cheers,
KnifeChick
 
My father has used Case/Buck knives for years which is 420. To shapen them he uses a set of three benchstones. I don't know how, but he gets them scary sharp in no time.

Whatever you use, I would suggest coating it with oil because 420 and 440 will clog up a stone fast.
 
A burr (wire-edge) forms when the two sharpening angles (bevels) meet. It indicates that the grinds on both bevels are approaching intersection. The metal folds over to the opposite side of your last sharpening stroke, or is simply it left as a rolled 'wire' along the edge.

It is an indicator of proper sharpening but can produce a 'false sharp' edge. The wire can feel very grippy on the back of a fingernail, and can be an ideal edge for cutting soft materials like meat. But for a durable push cutting edge, the wire must be removed. This can be accomplished by stropping, or by very lightly dragging the knife along a fine stone at a fairly steep angle away from the edge.

A wire edge should be produced at every sharpening grit. As you move towards smaller and smaller grit sizes (bigger grade numbers)the size of this burr will get smaller and smaller.

You question was 'to burr or not to burr'. I think creating the burr is essential. It is the most reliable way to tell if you have honed the primary cutting bevels all the way out to the edge of the metal. Stopping short of creating the burr will leave a relatively thick edge that will not last long. What kind of steel is being sharpened does not matter at all. All knife steels are malleable and ductile. They will all produce a wire edge during sharpening because sharpening is not only removing metal, but pushing it around.

Marking the edge with a black felt tip marker to help see if the bevels are ground sufficiently is another method that works well. I hope this helps a little
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Paracelsus
 
I vote for diamonds and water, rather than oil. I use a large coarse diamond bench hone working under running tap water above the kitchen sink. If the blade is really dull I alternate doing about 50 strokes per side until I start to feel a burr on one side. Then I work the other side till the burr runs 80% along the blade. Then I flip to the other side and work till I can get a burr on 95% of the blade. Then I switch to a large extra-fine diamond bench hone and alternate stroking left and right sides. I finish by stropping on plain leather.

The worst problems are on poorly heat treated 420 and 440. The chromium carbide grains are large and hard enough to impede the sharpening process. This is what gums up a hone extra fast. Soft hones have a hard time cutting these grains and giving a clean edge. There is a tendency to form a burr that doesn't get removed. Diamonds cut all the carbides cleanly and form a well defined edge. I use running water to keep debris from filling my hone and to cut the edge cleanly.

If I'm in a hurry I just use my belt sander for the rough work and finish with the extra-fine diamond diamond hone.
 
Welcome to the forums! I personally will bust out the Edge Pro and sharpen it with the ultra fine waterstone, then use a 3000 grit polishing tape. Mirror finish, very sharp!
 
Glad to to see another single digit poster!
I sharpen and repair for a living using the same water cooled belt grinder knives are made with, and I have to agree on the burr raising and removing. I know my grind is done when the 120 (80-100 for slicers) silicon carbide wet belt raises a burr,I then remove said burr with a cloth buffing wheel and buffing compound. On a stone i would only raise a couple degrees to remove a burr. Enjoy!
 
Great! Thanks everyone for your posts! Some really great feedback there and some useful information I'm going to definitely try out today. Had a "discussion" yesterday with two men about burr, they felt you should *leave* it on, the burr was that bad pieces of material would actually stick to the blade (it looked 'furry'). I nearly fell off my chair. Now I have some things to come back with from people who I have a feeling do a lot of sharpening
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Cheers and thanks again
 
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