The Burr: What is it and Why it’s Important
August 30, 2013
In my mind, sharpening is an almost ritualistic practice. You follow very specific steps, with predetermined actions until you finally produce the coveted sharp edge. Different sharpening methods and sharpening devices will require different sharpening rituals, but in the end the result is the same. Raising a burr is an essential part of any sharpening ritual. You may already do it without even realizing exactly what you’re doing. In that case you may be asking yourself, what is a burr and why is it so important?
A burr is a (plastic like) deformation of metal at the apex of the cutting edge. In other words, the burr is a small fold of metal on the other side of the edge you are grinding. Raising a burr lets you know that you have ground the edge thin enough on one side, to create a single plane of the bevel all the way to the edge. A burr also lets you know when to stop sharpening on one side of the bevel and switch to the other side. If a burr is not formed during the sharpening process then you haven’t fully sharpened the edge of the blade and your blade will not be as sharp as it could be.
Forming a burr can be troublesome, especially if you are trying to reprofile a bevel with coarse stones. If you use too much pressure when sharpening on a coarse stone, the burr will deform much larger than is necessary or will not form at all. Using more pressure decreases the likelihood of keeping a consistent angle when sharpening, which will directly affect your ability to raise a burr. In some cases, a burr can be directed downward, away from the edge and will form what is called a “wire edge”. The wire edge will seem incredibly sharp but is also very fragile and prone to chipping and falling off. This will leave your blade completely dull. Using light pressure and keeping a consistent sharpening angle is the best practice when “chasing the burr”. It may take more time but it’s a part of the sharpening ritual. If you rush or ignore this step, your final results will be less than perfect.
As I’ve discussed in other posts, the act of sharpening is really about trading a burr from one side of the edge to the other using progressively finer stones to polish away the burr formed by the previous, coarser stone. First you form the burr on one side, polish the burr away on the other side and continue sharpening until you form another burr. Once you have formed a burr on each side using your coarsest stone then you can progress to using finer and finer stones to polish and reform the burr until you end up with super tiny burr that often can’t even be felt. This final burr (which is often a wire edge) can be polished off with a high grit stone or a leather strop.
Hopefully this will help you understand the sharpening ritual better. Now you can start applying this knowledge to sharpening and start getting better results than you have in the past.
Be Smart, Be Safe and Stay an Edge Above the Rest
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