Detecting the burr

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KennyB

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Jan 19, 2010
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I've been using my fingernail to feel out the burr for a while, but lately I noticed when using a headlight that there was a small burr on the edge that I was actually pushing off when checking with my thumbnail.

I know of the whole 3 finger test thing, but I can't ever feel them when doing this. I think my fingers are just too messed up from playing guitar and stuff, because even if I raise a huge burr that I can feel easily with my fingernail I really can't feel it with the finger 3 finger method.

I was thinking that there was probably some other ways to see if the burr was there, just wondering if anyone had some recommendations. I think that using the headlight and my thumbnail will still be good for now, but if I can detect the burrs without knocking them off I think it'd probably save me some time.
 
I hope the experts will chime in soon but one guy(I forget who) said it's easier to see a burr with bright light than to feel it. I also got a jeweler's loupe to get a better look at what is happening to the edge while I sharpen.
 
Bright light and looking at the edge from as man direction as possible is one of the best ways and will even show you the burrs that are simply too small to feel. For larger burrs you can use the top of your finger nail, holding the blade near or at a slightly raised edge angle strop the surface of your nail down the entire length of the blade. If there is a burr present the side being dragged will scrape the surface of the nail or feel rough. This method is very effective down to extremely fine grits but can be deceptive because of the way some steels form a burr. Example: As you notice your nail was moving the burr.

Once you understand what to look for bright light and the occasional nail strop have been the methods that I have found to show the most detail. Even in the ranges of 0.5-0.25 micron.
 
One method that's worked for me, probably more often than any other, is to wipe the edge of your blade with a folded, damp paper towel. Wipe it very lightly in a 'stropping motion' (from the spine towards the edge), on each side of the blade. If a burr is there, it'll 'snag' the fibers of the paper towel as it passes over the edge. Usually it's obvious (you can feel the paper towel hang up at the edge), but even when it's less so, you can see the paper fibers being snagged & collected along the edge at the location of the burr. Use a magnifier and look for those little fibers clinging to the burr.

Keep in mind, the burr is basically a very thin and very ragged sliver of metal, which will likely be 'leaning' towards one side of the blade or the other. It'll tend to grab/scrape/scratch anything soft or fibrous that rubs into it. Occasionally, I've noticed, when stropping on very soft leather, the burr will scrape off & collect little bits of leather (and compound, if you use it on your strop). That's another indicator of the burr's presence.

Another suggestion, you might very lightly 'strop' the bevel along something very smooth & soft (like a wax candle, for instance). If a burr is there, it'll definitely scrape some of the wax off & collect it along the edge of the blade where the burr is. Imagine if you were 'scratching' the candle with your fingernails (i.e., burr leaning into the candle's surface), they'd collect wax underneath them. If you were to do the same thing with the 'back' of your fingernails (i.e., burr is leaning away from candle's surface), you'd be much less likely to scrape off any wax. The burr will behave similarly.

There's a few of my suggestions. Good luck!
 
I like using the "three finger test" Basically you use your pointer,middle, and ring finger to feel for a burr. It works extremely well for me.

I also find that with a belt sander, its usually easy just to see the burr.
 
I run the knife very easy on my strop and look at the results on the strop, if there is a burr you can see it in the strop.
gary
 
you can check for a burr real easy by using a new sewing needle. by pushing the needle to the edge, it will catch on the burr if one is present.

another way is to draw the edge across your thumbnail while pushing the blade away from you. if there is a burr, the blade will slip off your thumbnail.

the method i use most of the time is to hold the knife spine down to the floor and look for a shine on the edge under a good light. if you dont see anything, chances are you dont have a burr.
 
I do the dragging the blade on the thumb nail and the bright light reflecting off the burr as well . Only the big burrs coming off the coarse stone can I actually 'feel' . Once I progress to finer stones I cannot 'feel' it any longer . So, the head set with 5X and looking at the edge facing me under bright light will allow me to see it . Often its not a continous line along the edge . It mostly appears as segmented tiny needle point spots along the edge in places . When you see this your close . Progress to a finer grit and lighter pressure which further reduces the burr and then stropping will remove the remainder . DM
 
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