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View Full Version : Thumbnail, the most important sharpening tool



Fred
01-08-2005, 10:29 AM
I hear and read about sharpening problems all the time. Most of them relate to the problem of the sharpener not knowing how he or she is doing as they go through the sharpening process. The edge itself will tell you how it's doing if you are willing to listen, or rather to feel.

Do this experiment. Take a sharp knife and give it a light swipe on one side of the blade. Then place the edge lightly on your thumbnail at an angle, not straight up and down. You will notice that, in one direction, the edge will have very little feeling and on the other it will catch a little.

The side that catches is the side that has the burr. It is the side opposite the one to which you applied the steel. Now go back to the steel and take a swipe on the side that now has the burr. The thumbnail will tell you that the burr is now on the opposite side.

That's lesson number one in learning to communicate with your edge. The burr is nothing more than the very thin end of the edge which has been turned over from contact with the steel. It isn't terribly important to cutting but it is important because it communicates a lot to you about how your sharpening is going.

If a light swipe in each direction didn't turn the burr as I described then we already know the knife needs sharpening. If the burr is inconsistent along the length of the edge then we know you didn't finish some step along the way as you sharpened it. Impatience is the primary cause of poor sharpening.

As you progress through the finer grits of abrasive you will notice that the burr becomes thinner and harder to feel. Once you get to around 12,000 grit on a waterstone, there won't be much burr left and it will be very hard to feel. All this tells you is that the edge is getting smoother and smoother as you progress through the grits.

With very little practice you'll be able to tell how sharp a knife is just by feeling that burr. So, if you have problems sharpening, learn to communicate with the edge. It will guide you toward better results. Good cooking.

RETREVR
01-08-2005, 10:51 PM
Yep. Nobody taught me how to sharpen. Years ago I would just work each side of the knife on the stone untill I thought I had a sharp knife. This is like pissing in the wind.
Understanding the bur and being able to recognize it is the first step to becoming proficient at sharpening. Some knives take a long time to raise a bur. Some take two passes. Depends on the steel and the condition of the edge I suppose.

Richard
01-08-2005, 11:20 PM
Thanks for the info...I've heard you mention the thumbnail tip a couple times before and I was always a little fuzzy on the details. It's all clear now.

**DONOTDELETE**
01-09-2005, 10:18 AM
This sounds like the second use of the thumbnail...the first way sounded like giving your nail a slight 'tug' against the blade - in the cutting direction, or from edge to spine (?) as a way to see if the edge is sharp. Are you also saying that in checking the progress of sharpening, checking the development of the burr, you pull/slide your nail in a downward direction or from spine to edge ?direction? /ubbthreads/images/graemlins/confused.gif

Fred
01-09-2005, 11:18 AM
No, I just press the edge against the nail lightly and I don't move it. No need to cut anything.

Ken
01-09-2005, 12:35 PM
I usually feel the burr with the flat of my thumb rather than my thumbnail. I gotta try it your way sometime, Fred.