How much of a burr?

K

KC8QVO

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Apr 7, 2011
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I just have to ask this. Maybe I will be in the same position I am now after this thread, but at least I'll take the initiative and ask :D

How much of a burr should be worked up before finishing and edge????

What I do is, if I am just touching up a knife, run a couple passes with my EP Apex to where one side feels "rougher" than the other. Then I finish the "rough" side with a swipe of the stone against the blade with just the weight of the stone. Then I switch to the next highest grit.

If I am re-profiling, or otherwise need to knock off more material, I will use a low grit (120 if its a hard grind, 220 is where I will usually start). I will make a few passes. With each pass I flip the blade and even out the grind. Once I get a workable edge I will finish the "rough" side again with a pass of light against-the-blade swipes of the stone and progress just like I do touching up.

I have never worked up a burr I can really see. This brings me to my core question. How much of a burr should there be? Should it be enough to see or something you have to rub your finger across to "feel"?
 
This is what works for me.

I raise a distinct burr below 320 grit. Above 320, I use the digital microscope to assure that I'm getting to the edge.

If you create a burr on both sides at 320, you've come all the way to the edge, and from that point on, you're refining the edge, so no burr is necessary, or in my experience, desireable.
 
If you've worked up a burr you should be able to see it atleast w/ 5-8X magnification in bright light. A larger one you can feel. DM
 
i only work up enough of a burr to form a good edge. if you look at post 890 in my paper wheel thread above your post you will see how much of a burr i work up on a knife. i have two other pictures showing a rather long burr i did on purpose.
 
The burr can be as small as is possible to detect, either by feel or by sight, with a magnifier or microscope, if necessary. SO LONG AS the burr runs the full length of the cutting edge. It's pretty easy to raise a burr on only a portion of the edge, but oftentimes the tip and sometimes the heel seem to take longer to get there. Big payoff at the tip, especially, in making sure it's fully apexed.

Depending on the steel and the sharpening method, sometimes burrs will be harder to detect. That's when it's really a big help to closely examine the edge with as much magnification as possible, with very bright light. If you still don't see a burr, per se, then at least watch for the apex of the edge.

It's generally MUCH easier to raise a distinct burr at low grit, as Ben pointed out. Much easier to see it, and it will make the following steps a lot simpler, in removing the burr & refining the edge. Even if it seems the burr is obscenely large, it's still definitive proof that the edge has been apexed. With more practice and knives sharpened, you'll get better at detecting the burr when it's just beginning to form. With some steels, you'll even be able to feel it against the hone, at the moment the apex of the edge 'bites' into the abrasive surface. As soon as you feel that, STOP and take a close look for the burr.
 
Richard,

Your post with the pictures is partially what sparked my question. With the use of the Edge Pro system, or any other wet stone/slider set up, the stone is passed both directions over the edge - towards and away. I would assume that pushing the stone back across (towards) the edge would not increase the burr, whereas dragging the stone off the edge would "pull" metal from the edge around the apex and create the burr. Is this correct? Based on that assessment, the only way I will create much of a burr is if I pass the stone away from the edge all the time.
 
KC8QVO said:
Richard,

Your post with the pictures is partially what sparked my question. With the use of the Edge Pro system, or any other wet stone/slider set up, the stone is passed both directions over the edge - towards and away. I would assume that pushing the stone back across (towards) the edge would not increase the burr, whereas dragging the stone off the edge would "pull" metal from the edge around the apex and create the burr. Is this correct? Based on that assessment, the only way I will create much of a burr is if I pass the stone away from the edge all the time.
Click to expand...


I have used the Edge Pro for over a year, and I can definitively say that both motions will result in burr formation, as long as you are reaching the apex of the edge. :)
 
Obsessed with Edges said:
The burr can be as small as is possible to detect, either by feel or by sight, with a magnifier or microscope, if necessary. SO LONG AS the burr runs the full length of the cutting edge.
Click to expand...

The burr should be just large enough to completely regrind the bevel all the way to the apex - it needs to be continuous the full length of the cutting edge. If the knife has been sharpened properly after leaving the factory, the burr can be quite small and still reveal a new apex. The first sharpening coming from the factory and that burr might have to be fairly large to smooth out the bevel along the entire length. The larger it gets the harder it is to remove, so if I see a lot of work to be done I'll raise and remove several times till I'm getting a good clean edge with no areas sporting largish burrs while other areas are still untouched. Managing and eliminating the burr is one of the most important skills in the grinding portion of edge sharpening - very easy to mess up an edge chasing a burr from side to side, but it must be done. The smaller the burr you create, the fewer flips needed to remove it, less chance of widening your inclusive angle.

Pretty much any repeated movement of steel on a fixed abrasive can create a burr- be it stone, sandpaper, etc. Edge leading eats some of the burr material up as it goes, edge trailing leaves more of it hanging off the end. In my experience, it is virtually impossible to completely remove a burr using an edge trailing motion on a fixed abrasive - very careful grinding can remove all of the burr using an edge leading stroke, but even this is quite difficult - that's where your strop comes in.
 
a trailing edge stroke will bring up more of a burr like hh said which is how i have always sharpened a knife even by hand.

most of the time when i work up a burr i can hardly tell i have one. sometimes i can use the back side of my fingers to feel the burr as i pull the blade flat up to my fingertips. when you get a chance to stop down i'll show you first hand what i mean and teach you how to use the paper wheels too.

in the first picture of the burrs in my paper wheel thread, i made the burr on the knife edge a little bigger than normal so it would show up.
 
A burr is a plastic deformation of metal that is heavily influenced by pressure, more pressure more burr less pressure less burr.

When setting a bevel the burr should be raised as a sign the apex has joined and then it should be removed by the same stone before progressing. By removing it with the same stone you will be able to tell if the apex is fully joined and if its time to progress to the next stone. Each following stone should not produce as large of a burr because you are not trying to intersect the apex, the burr that does form should be debris and excess deformations from the scratch pattern being removed by the finer stone.
 
kc8qvo, when you come down, bring everythign you have to sharpen and what you have to sharpen with including any stones. (i emailed you some links to check out that will have you rotflyao too ^^)
 
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knifenut1013 said:
A burr is a plastic deformation of metal that is heavily influenced by pressure, more pressure more burr less pressure less burr.
Click to expand...
Nevermind I got my answer.
 
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Thanks Richard. I appreciate your help.
Thanks to you my straight razor shaves better than ever.
 
Should you accidentally get a burr at the higher grits, it's easily removed by lightly drawing the blade on the end of a piece of pine, or if it's a high end steel, slice a small sliver of leather from a piece of scrap. :thumbup:
 
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