what is a burr?

[Legenda]

Thats all im asking, what is a burr?

 

[dericdesmond]

http://www.bladeforums.com/forums/showthread.php/697747-The-burr

 

[dantzk8]

A dull edge is "U" shaped. A sharpened edge is "V" shaped. To go from "U" to "V" you have to go by "Y" by thinning the edge. The tail of the "Y" is a burr.

dantzk.

 

[richard j]

here are a couple pictures of a burr.

 

[Obsessed with Edges]

The above posts are all good and, additionally, keep in mind that burrs can vary greatly in size. That big, honkin' burr shown in Richard's pic is a good visual, but many or most times, burrs will be smaller (much smaller, I hope ). It'll usually be easier to feel it, as opposed to actually seeing it, by sliding a thumbnail down the blade's side, towards the edge. A burr (or wire edge) will usually catch the fingernail. Same could be done by sliding a sharp toothpick or needle tip towards the edge, and it'll stop against a burr/wire there, on the side that the burr/wire 'leans to'.

'Wire edge' usually refers to a burr that runs continuously along the length of the edge. A 'burr', on the other hand, might sometimes only be an isolated 'tatter' of steel in a small section. Many here use the terms somewhat interchangably. They both essentially imply the same thing: the edge has been thinned enough, at that location, to make the steel sufficiently flimsy/weak to allow it to fold over. When you see/feel it, that's the indication that the edge has been 'apexed' (both sides ground to make the bevels meet in a sharp intersection).

 

[parbajtor]

Unless you're talking about wood, in which case it is an abnormal growth on a tree usually following parasitic attack.

 

[richard j]

i made the burr on the putty knife long so it would show up better. here is a picture of a small burr which is probably more than what is needed to get a knife sharp. i made the burr in this picture longer also so it would show up. i cropped the picture so that portion of the edge is roughly 1 1/2" long and the burr is roughly the size of a human hair.

 

[richard j]

Unless you're talking about wood, in which case it is an abnormal growth on a tree usually following parasitic attack.

you must be thinking of a burl http://www.bladeforums.com/forums/showthread.php/896379-i-found-a-huge-burl?daysprune=30

 

[Obsessed with Edges]

Actually, the 'wood' reference made me look it up in my dictionary (Random House Webster's Unabridged). I wasn't aware of it previously, but here's one of the accepted definitions for 'burr':

"a rough or irregular protuberance on any object, as on a tree."

And from Wiki, for 'burl' --->: http://en.wikipedia.org/wiki/Burl , with a pic here --->: http://en.wikipedia.org/wiki/File:Corsehillburr.JPG

"A burl (American English) or bur or burr (British English) is a tree growth in which the grain has grown in a deformed manner. It is commonly found in the form of a rounded outgrowth on a tree trunk or branch that is filled with small knots from dormant buds."

Learned something new once again.

 

[richard j]

i never heard a burl called a burr. same here on learning something new .

 

[dantzk8]

That big, honkin' burr shown in Richard's pic is a good visual, but many or most times, burrs will be smaller (much smaller, I hope ). It'll usually be easier to feel it, as opposed to actually seeing it, by sliding a thumbnail down the blade's side, towards the edge. A burr (or wire edge) will usually catch the fingernail. Same could be done by sliding a sharp toothpick or needle tip towards the edge, and it'll stop against a burr/wire there, on the side that the burr/wire 'leans to'.

A burr can even be so tiny you will not notice it with a fingernail. But if you can shave your arm hair on one side of the blade and not on the other one then you have a burr.

dantzk.

 

[HeavyHanded]

Verhoeven describes another type of burr as well. The steel directly behind the apex can bulge outward from impacting the abrasive field - this is most common on coarser grits and I've seen it on steel as tough as 154cm and Sandvic.

 

[Obsessed with Edges]

A burr can even be so tiny you will not notice it with a fingernail. But if you can shave your arm hair on one side of the blade and not on the other one then you have a burr.

dantzk.

Yes, good point. :thumbup:

(in fact, I've seen that one a lot. Troublesome li'l buggers, aren't they?)

 

[richard j]

i have had knives sent to me for sharpening and chip removal. i had a burr worked up on a knife one day removing a chip that was over 1/8" long. they get soft as baby skin believe it or not when they get that long due to how thin they are.