am i doing this right

[wwells20]

I have never had a problem seeing a burr. Just got to have the angle and light right.

Burr below was formed on 220 grit.

This is how my burrs look. All you have to do is sharpen one side of the blade untill it looks like this and then do the other side. You just have to twist the blade just so and you can readily see this burr. Thanks for the pic. Nosmo.:thumbup:

 

[Cliff Stamp]

Thanks for clearing up how you define sharpness... guess it is just different than how I define it.

It is common to interchange sharpness and cutting ability. Mike Swaim was the first I read on the internet separate them (about a dozen years ago). In so doing he exposed a number of myths about knives. Primary among them was the fact that you can get better edge retention at lower edge angles because a knife will continue to cut better at a lower sharpness due to the effect of the reduced angle on cutting ability. You could never even consider this arguement if cutting ability and sharpness were equated.

Imagine taking your sharpest knife and grinding straight into the edge so when looking right into the edge it was 0.1 mm wide. Now even if the angle is very low, even if the grit is very high (or low) it doesn't matter. Such an edge scores basically a zero on any test of sharpness. Thus all that is critical to sharpness is the state of the last sub-micron part and specifically the level of abrasion vs deformation/fracture. As metal is deformed or fractured above the size of the abrasive it lowers sharpness.

...you're the only one I know that has started defining primary and secondary burrs.

I can't take credit for that distinction it is well known in wood working. The primary burr is debris and weakened steel left on the the edge from the grinder. A secondary burr or edge deformation bias is actually intentionally formed on some tools. They don't use those labels specifically, they are usually called a burr and a hook. On knives the hook is usually not intentional or desired but will readily form on ceramic rods due to the high contact pressures, the exact same way it forms on a scraper using a burnisher. There is also a third kind of burr which is caused by fracture and distinct both in its properties and how it is avoided. A better set of labels would be debris, deformation and fracture burrs.

"At some level" you'll always have deformation.

Yes and the extent of the deformation/fracture dominates the measurements of sharpness and edge retention. The more you reduce it the sharper the blade will get. It isn't a binary switch which is on or off, but more of a linear responce. Minimizing the burr is easier on some steels as it depends on the grindability*strength product. Carl noted this sometime ago on rec.knives. The general idea is commonly known but he was the first to suggest you could rank steels numerically by using the relevant materials data and cited H1 as a steel which had a nice balance of properties.

You would also need to include the effect of grain size and this depends on if you are aiming for a coarse or polished edge. So a rank would be something like grindability*strength/grain size for polished edges for push cutting and grindability*strength*grain size for coarse edges for slicing. So for example you can still have a very high ease of sharpening even with a low machinability if the strength is very high which keeps the edge crisp.

-Cliff

 

[tim8557]

Flame me if you will folks but I have to say this...

What the hell is Cliff talking about?

Seriously, I've read and re-read all that has been written and like usual I have no idea what he's saying. Is this just me or is he arguing to argue? Maybe I'm too stupid to understand or he's too smart to explain?


--Dave--

It's okay Dave. I believe that Cliff has a PhD or is working on one. My son has a PhD. PhD'ers speak in code not decipherable by us common mortals.

 

[cbwx34]

Amen. My point exactly. Everytime he posts... it takes ten more to figure out what he really means.

 

[Cliff Stamp]

... not decipherable by us ...

All you have to do is take the red pill, Mike Swaim's posts on rec.knives will tell you where to find it. I will warn you though, if you do, you can never go back and you will also look upon pretty much every knife that you handle as in need of severe edge reconstruction so it isn't a club. If you take the next step and dare to read possums posts on dymanic/static balance it gets even worse and now you will want to hack off all that unnecessary metal in the tang and grind in some tapers to the blade. The choice is yours, take the blue pill and live in the world of "optimal" 20 degree highly polished edges or take the red pill and explore the limits of performance. I don't have the pills as noted, I am just one of the many that Mike gave them to.

-Cliff

 

[kel_aa]

What was Rec.Knives part of before it came under Google?

And how do you view Rec.Knives? Is there some secret I'm missing? The format and layout is a real pain in the butt.

 

[Cliff Stamp]

It was (is) a usenet group, not to be confused with the online forum which was recdotknives (long defunct). Threaded newsreaders make it easier to interact on usenet, like tin. I use Pine, but I am old school and still use lynx. For those considering viewing, rec.knives is not moderated and there is *NO* tolerance for hype at all. You also need an active killfile as with all usenet there is a lot of cross flame/spam, usually heavily racist. With a few selective personal bans you can focus on the knife discussion.

Kevin Cashen by the way is giving out his own fair share of red pills :

http://www.cashenblades.com/articles/The anatomy of hype.htm

"I sincerely believe that one of the reasons that steels of the month are so hot for a short time is that the guys pushing it make their quick buck before folks actually use it enough to realize it is just another steel with no magic at all. Fortunately for the scam artists that offer the steel of the month, those disillusioned masses never totally snap out of their trance, but instead grab onto the next steel of the month hoping to replace the short of promised performance with the new hot steel that is the “real deal”. If one ignores the clamor and looks at the big picture, campy fad steels come and go but there are a few boring old favorites that have been working great for knives forever, and why is this? Because they work, they are too common to be sensationally unique for they were designed by industry to cut things and they do."

-Cliff

 

[kel_aa]

This is how I find it:

Go to Google, click on Google Groups, and search for rec.knives.

And a post looks something like this:

Notice only a little of the screen width is used for the actual message. and the use of > gets annoying as, as you get to >> and >>> for double and triple quotes. Can you post a screenshot of how view it?

 

[db]

do a search for free usenet servers. There are a few web based that you can read usenet groups with your brouser. some are good and some aren't. You can also read the groups with your email program like Outlook if your ISP carries them witch it most likly does. Check your email help for news groups to find out how.

 

[Cliff Stamp]

Can you post a screenshot of how view it?

Same way, except much simpler as I use pure text based, email lists are the same way. It used to be the standard for web-based discussion but compared to the graphical presentation of modern BB based discussion forms it is very awkward to manipulate and cumbersome. As there are no graphics and everything is pure text there are no colors or ability to bold/font, so the ">" are standard for quoting. The advantages are speed as there is no graphical overhead, and of course no moderation and thus no monetary bias. No one owns usenet and thus everyone has an equal say. This of course gives trolls freedom as well but as soon as they are ignored they dissipate. It used to be much more active however much discussion has moved to the graphical based discussion forums which have many advantages but since they are owned they have limitations, some more than others.

-Cliff

 

[GibsonFan]

I've always used the back of an old leather belt to strop off that fine burr. If it's not huge, the leather will polish it right off with a little p[atience and leave a nice clean sharp edge. Works for me

 

[omniphile]

I can only reinforce GibsonFan's comments. I got some absolutely fantastic advice from Cliff and frugalweaver (on http://www.bladeforums.com/forums/showthread.php?t=409948), and for about $10 my knife sharpening is about 100% better.

The people here really have great advice.

 

[HoB]

Flame me if you will folks but I have to say this...

What the hell is Cliff talking about?

Seriously, I've read and re-read all that has been written and like usual I have no idea what he's saying. Is this just me or is he arguing to argue? Maybe I'm too stupid to understand or he's too smart to explain?


--Dave--

What is it, that you don't understand, and where is the argument here? I don't think that anybody has been arguing in this thread. Cliff gets occasionally in arguments, but I don't see one here?

Maybe I can translate: Cliff simply said that you have to pay attention to the burr and that the burr is not unique to coarse grit sharpening. Only that you usually see/feel it when sharpening with coarse grit more readily.

Later the discussion when to sharpness. Cliff says that sharpness is not dependent on angle or grit finish. What he refers to as "sharpness" is how well formed the edge is. However, cutting ability is highly dependent on the both on finish and edge angle/relief angle. Even if the edge is sharp (well formed) but thick, cutting ablity will be low (imagine using very sharp scissors using it like a knife). On the other hand, if the angle is low but even if the edge is not really well formed it may cut resonably well (example a SAK), Same if the edge is sharp (well formed) but coarse, pushcutting will be mediocre, but pull cutting will be good. He is also referring to the fact that you can get a very well cutting coarse edge, but that it is very difficult to get a well formed (sharp) edge with a coarse medium since the burr will form so readily.

Finally the discussion went on to primary and secondary burrs, terms that I have not encountered before, but Cliff has explained what he means. The primary burr is what you usually consider the common burr that you get from sharpening. According to Verhoeven it is consists of debris (metal carried to the edge or pushed away from the edge and abrasive welded to the edge). What he calls secondary burr is a deformed edge. First you form a sharp edge (well formed) but during use the edge deforms and bends over forming what looks like a burr but it's made up is good steel, not debris.

Cliff also mentioned early on, that burrs are easier to see, when they are bent one way or the other. If they are perfectly aligned with the edge, they are more difficult to detect (not sure if I agree with that).

All in a nutshell, of course.

Does that help? (Cliff, feel free to correct me if you feel I misrepresented what you said)

 

[Cliff Stamp]

What he refers to as "sharpness" is how well formed the edge is.

Yes, specifically the level of abrasion vs deformation/fracture. This is an expansion of Swaims distinction of sharpness and cutting ability. I used to say it was a matter of alignment, which is true, but I think the current defination is more fundamentally sound and as well as notes specifically the physical properties involved.

-Cliff

 

[HoB]

specifically the level of abrasion vs deformation/fracture. -Cliff

What exactly do you mean by that. Are you referring that an edge is mostly dulled due deformation and fracture and not so much by abrasion?

I would say that for the definition of sharpness it really shouldn't matter what the causes for the poorly formed edge is. Whether the edge is rounded (the two planes not meeting), deformed or fractured.

 

[Cliff Stamp]

I would say that for the definition of sharpness it really shouldn't matter what the causes for the poorly formed edge ...

True, however if abrasives induced no deformation/fracture[*] then all you would have to do is sharpen until the edges would meet and you would be done at perfect sharpness. If you are honing on a ceramic rod and the edge is just getting pushed to one side and the other, then the reason it is not getting sharp is that the level of deformation is high.

An edge with a low level of deformation and fracture which has been abraded until the bevels meet (this is just shaping and not sharpening) has to be optimally sharp. Some methods of sharpening actually work by deformation and others by fracture, knapping and steeling for example. But generally most discussions are on some type of abrasive which is where the above defination applies.

-Cliff

[*] If you want to get technical, abrasion is deformation/fracture, when separating them I mean deformation/fracture beyond the size of the abrasive. Similar to separating cutting vs breaking something.

 

[Cliff Stamp]

As an example of why I feel separation of such issues as noted in the above is helpful I'll describe a recent sharpening experience. I had ground a Delica in ZDP-189 down to less than 10 degrees per side. I had intended to go all the way down to primary but the grindability of ZDP-189 is low and I stopped leaving the grind almost full on one side and with a light convex bevel of about 18/20 included in the last 0.030" thick. Applying a microbevel at 15 with a 600 DMT the burr formed readily and persisted even after a higher honing and reset. Knowing it was just a case of too much deformation and not enough abrasion I switched to very short honing passes, about half a cm or so, working the edge in sections and flipping after each pass. Essentially the burr is cut off immediately on a pass once the edges have met and thus honing on the same side tends to induce deformation so optimally the honing is just enough to abrade. This reduced the deformation significantly and enabled smooth shaving on both sides.

-Cliff