Burr or Wire edge ?

G

Great Steel

Joined
Jan 14, 2016
Messages
29
I could use some help . What is the difference between a Burr and a Wire edge ?

Thank you !

Great Steel
 
Here's my take:

A burr is dud metal that clings to the boundary of a ground surface. On a knife edge it forms on the opposite side of the grind. No abrasive is 100% efficient, so some of the steel is left behind as it passes into space - no support behind to grind it off entirely as with the rest of the bevel. It falls outside the geometry of the edge.

A wire edge is a fin of steel that also falls outside the geometry of the edge. It can begin life as a large burr that gets finessed instead of being ground away, or it can happen on thin blades as the edge flexes away from the source of grinding pressure. It gets ground behind the apex, removing the support steel. Visually you can see that it does not throw light back on the same plane as the rest of the edge, flip it over and the same thing is observed on the opposite side.
 
HeavyHanded said:
Here's my take:

A burr is dud metal that clings to the boundary of a ground surface. On a knife edge it forms on the opposite side of the grind. No abrasive is 100% efficient, so some of the steel is left behind as it passes into space - no support behind to grind it off entirely as with the rest of the bevel. It falls outside the geometry of the edge.

A wire edge is a fin of steel that also falls outside the geometry of the edge. It can begin life as a large burr that gets finessed instead of being ground away, or it can happen on thin blades as the edge flexes away from the source of grinding pressure. It gets ground behind the apex, removing the support steel. Visually you can see that it does not throw light back on the same plane as the rest of the edge, flip it over and the same thing is observed on the opposite side.
Click to expand...

Hi HeavyHanded


Thanks for clearing that up !
So I'm thinking it's a wire edge I'm ending up with in my return to sharpening, I think !
I sharpened my own knives for many,many years in the meat trade but now I seem to be having a glitch. After using a medium grit waterstone with around a 20 degree bevel I have removed any major burr. I then switch to a very hard Scottish stone called a "Water of Ayre" repeating the process I used on the medium grit waterstone.

I now have no burr on the knife edge that I can feel. The knife edge will hang on my thumbnail, the edge will slice paper easily on the pull stroke, but not on the push stroke. The knife edge will somewhat shave hair off my arm but by no means is it hair popping !

Any ideas for getting my edge sharper ? Are you reading anything that I'm doing wrong ?
Thanks
Great Steel
 
Great Steel said:
Hi HeavyHanded


Thanks for clearing that up !
So I'm thinking it's a wire edge I'm ending up with in my return to sharpening, I think !
I sharpened my own knives for many,many years in the meat trade but now I seem to be having a glitch. After using a medium grit waterstone with around a 20 degree bevel I have removed any major burr. I then switch to a very hard Scottish stone called a "Water of Ayre" repeating the process I used on the medium grit waterstone.

I now have no burr on the knife edge that I can feel. The knife edge will hang on my thumbnail, the edge will slice paper easily on the pull stroke, but not on the push stroke. The knife edge will somewhat shave hair off my arm but by no means is it hair popping !

Any ideas for getting my edge sharper ? Are you reading anything that I'm doing wrong ?
Thanks
Great Steel
Click to expand...

Is the Scottish stone a fine silt stone or is it hard like a form of Novaculite? If it is a hard stone and not very abrasive it can sometimes act as a fine steel instead of a stone - more burnishing than material polishing/removal. Any residual burrs no matter how small will be pushed into evidence, and even if 100% burr free, the steel could be getting drawn out into a wire. This is particularly easy to do on lower RC steel. A wire edge will often fold just like a burr once it gets used and will make for inconsistent sharpening.

Maybe coming off the med waterstone (and if it IS a hard smooth stone) limit yourself to just a few super light leading passes on the Water of Ayre stone at a slightly higher angle. If you are consistently stymied, I'd stop using it or lapp it before using any more.

A nice alternative for casual sharpening might be to tap/smear a bit of mud from your waterstone onto a sheet of paper and let it dry. Wrap that around a dry stone or similar and strop on that instead of finishing on the Scottish stone and see what happens. I've also (in the kitchen primarily) been known to smear a bit of wet waterstone mud right on a cutting board and strop on that, not even letting it dry out. You'd be surprised how quickly a nice edge can be whipped up in this manner and it rinses right off.
 
HeavyHanded said:
Is the Scottish stone a fine silt stone or is it hard like a form of Novaculite? If it is a hard stone and not very abrasive it can sometimes act as a fine steel instead of a stone - more burnishing than material polishing/removal. Any residual burrs no matter how small will be pushed into evidence, and even if 100% burr free, the steel could be getting drawn out into a wire. This is particularly easy to do on lower RC steel. A wire edge will often fold just like a burr once it gets used and will make for inconsistent sharpening.

Maybe coming off the med waterstone (and if it IS a hard smooth stone) limit yourself to just a few super light leading passes on the Water of Ayre stone at a slightly higher angle. If you are consistently stymied, I'd stop using it or lapp it before using any more.

A nice alternative for casual sharpening might be to tap/smear a bit of mud from your waterstone onto a sheet of paper and let it dry. Wrap that around a dry stone or similar and strop on that instead of finishing on the Scottish stone and see what happens. I've also (in the kitchen primarily) been known to smear a bit of wet waterstone mud right on a cutting board and strop on that, not even letting it dry out. You'd be surprised how quickly a nice edge can be whipped up in this manner and it rinses right off.
Click to expand...

HeavyHanded

Thanks for your reply !

The Scottish stone is very hard, not very porus if at all. I will try the tips you have mentioned above

Thanks Again
Great Steel
 
Update !

So this is what I tried and it worked quite well ! I backstroked the edge on GatorGrit 600-b waterproof paper several times both sides. Results seem real good .
Great Steel
 
I also have the same question. Some hand drawings showing the difference would really be appreciated.
 
Great Steel said:
HeavyHanded

Thanks for your reply !

The Scottish stone is very hard, not very porus if at all. I will try the tips you have mentioned above

Thanks Again
Great Steel
Click to expand...


Yeah, that stone is no good. If you'll pay the shipping, I will dispose of it for you. PM me for the address.

:D
 
sharp_edge said:
I also have the same question. Some hand drawings showing the difference would really be appreciated.
Click to expand...

I'm having a tough time illustrating this one...

Easiest way to get a good understanding is to drag or push a sharp object such as a crisp screwdriver tip or corner of a file across a piece of aluminum (it helps if you have a loupe or magnifying glass too). Stop in the middle on one pass, and on another line run it right off the clean edge of the aluminum. You will see that the tool tip carves a gouge, on either side of the gouge (and at the lead edge of the stopped one) there is partially dislodged metal.

The "abrasive" is not 100% efficient, there is dud metal left behind, and as it passes off the edge of the plate it leaves some hanging in space. It will also leave some hanging in space if you push the abrasive into the edge of the plate though a bit less than when it is dragged off - some of the metal simply deflects away or is gouged loose but not free of the underlying metal.

With an entire field of abrasive points, all the stuff in the middle of the area gets ground off by the neighbors, so what's left is the stuff hanging off the edge and maybe a bit on the shoulder.

Some things that influence burrs -

The angle another plane meets relative to the grinding surface - the shoulder is at a very broad angle, the abrasive digs into it with a much more gradual plunge - smaller burr than on the edge. Unfortunately for us, an acute meeting angle will be most likely to burr.

How rigidly the abrasive is fixed to the grinding surface. If the abrasive can shift as the burr is forming, it will deflect away if the digging resistance exceeds the holding force of the abrasive. Hard fixed abrasives will produce the largest burrs all else being equal, compared to stuff like sandpaper, waterstones etc. How friable the abrasive is will have an influence - if the force needed to break the abrasive is less than the amount of resistance it meets when embedding into the steel, the mineral will snap off and the burr growth retarded. Some lapping actions barely produce any burr at all - the only resistance to movement is the amount of force applied between the two surfaces and the texture of the two surfaces.

How sharp the abrasive is and its overall shape - the sharper the mineral the more cleanly it will shear off bits of metal.

Force - more pressure will cause the abrasive to dig deeper into the metal - displacing more per grind trough.


For the wire edge you just have to imagine the metal surface deflecting away from the force applied by the abrasive, or imagine a very large burr being worked ever finer but not removed at the attachment point. Either way it will look like a "Y", with the "edge" being the base - outside the geometry of the joined bevels.
 
You must log in or register to reply here.
Back
Top