Macro burr versus micro burr

D

DevinT

Joined
Jan 29, 2010
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There has been some discussion about sharpness and knives. The topic of burrs also came up.

A macro burr is also called a wire edge. It’s big enough to see and feel, they usually develop after doing the initial sharpening on a belt or a wheel.

A micro burr cannot usually be seen or felt. They are even difficult to see under magnification.

A macro burr runs the entire length of the sharpened edge. A micro burr can be sporadic and intermittent. (across the entire edge)

The finer the sharpening stone the finer the micro burr. This is why it doesn’t feel like there’s a burr when sharpening by hand.

Wayne Goddard recommends increasing the angle of the blade on the finishing stone and lightly drawing it to remove any burr and then do a few regular strokes to get it’s final sharpening.

I’ve seen guys use hard felt, pink eraser, hard wood etc. to pull the burr off. And then go back to the stone for a light resharpen. Not my favorite but works.

I like a loaded paddle strop for most knives and a hanging strop for straight razors.

Most of what I’ve learned about burrs is from using a straight razor and looking at the edge under magnification. A razor with a burr will tug on the whiskers.

Most knives feel sharp but still have a burr. Any burr will shorten the life of an edge.

Good luck out there

Much respect

Hoss
 
Is there not always going to be some level of micro burr?

I feel many people like to raise a macro burr then fight the burr through the rest of their sharpening.


I have been playing with 600 grit finishes and with alternating edge leading strokes I am not seeing a burr under 100x magnification though I am sure there is still one but micro.

Interestingly stroping on 1u diamond compound on micarta backed leather the BESS decreased 17% for a 600 grit diamond edge but did not change for a 600 grit water stone edge.
 
DevinT said:
I like a loaded paddle strop for most knives and a hanging strop for straight razors.



Good luck out there

Much respect

Hoss
Click to expand...

Mind sharing what you use on the strop...and are you finishing on the same strop? (Knives, not razors.)

Thank you.
 
I generally pull through a wine cork and/or a piece of balsa wood. I start with a strop loaded with green compound before moving to diamond compound loaded strops. I’m sure some of my steps aren’t necessary but I’ve always been happy with the results. I have loupes of various magnification and a microscope on my computer I use to see what’s going on if an edge gets stubborn.
 
I keep a couple of corks handy. I'm not necessarily convinced they do a great job...but I keep 'em around anyway.

Shouldn't the green compound come after the diamond?
 
Particularly for macro burrs, I’ve not found drawing an edge through wood or cork to have much of an effect. I generally go to finer grits and strop or increase the edge angle for a few passes to remove the macro burr. Micro burrs are somewhat of a mystery as I’ve not used a microscope for a long time for sharpening.
 
Blues said:
I keep a couple of corks handy. I'm not necessarily convinced they do a great job...but I keep 'em around anyway.

Shouldn't the green compound come after the diamond?
Click to expand...
I think the green I have is 3000 grit equivalent but don’t remember for sure. I go up to either 2000 or 2500 on stones. I’ve got 5 or 6 different grits of diamond compound and if I remember correctly they start at 5k. Corks generally work for me but I also use wood if needed. Realistically I probably don’t need to do most of what I do when I sharpen but I enjoy it and it’s cheap entertainment.

Magnification too often gets overlooked when it comes to removing the burr. Lots of people have a process to do it but no way to really look at it to confirm it works.
 
I recall hearing that Phil Hartsfield would make several cuts in hard cardboard to knock the burr off.
 
Might be blasphemy on this forum. Please don’t bring torches, crosses and burn my house. I use a cloth or rubber wheel on bench grinder with green or peach colored buffing compound the one that’s easiest to reach on my bench. I don’t apply enough pressure to get them warm. Knives stay cool to the touch. This works for me I’m not recommending that anyone does this but it’s never gave me a problem. For the knowledgeable knife makers on this site please let me know if this is slowly ruining my knives.
 
DevinT said:
Wayne Goddard recommends increasing the angle of the blade on the finishing stone and lightly drawing it to remove any burr and then do a few regular strokes to get it’s final sharpening.
Click to expand...
This is how I was taught and is still how I remove a burr most of the time. But, I have found that running the edge over wood is helpful on real stubborn burrs.
 
Like Hatch power, please don't judge me ... this is just how I resharpen most knives. I have all the fancy stuff, too, but this takes only a minute or two to do. I may go to stones on fancy kitchen knives or a skinner, but most knives just need a sharp working edge.

I use a 400 grit AO belt on knives that only needs re-sharpening. I run the belt slow and in reverse and work on the top of the belt between the upper idler and the tracking wheel. On the Reeder grinder I installed a short glass platen on the top and use a sharpening jig, but that is used mostly for setting the edge on a new blade. Most of the time I'm on the TW-90 and simply hold the knife by hand and judge the angle by eye and feel. After getting a good edge and even macro burr, I draw it down a 2X4 pine board on the edge of the bench to remove most of the burr. Then I buff the edge on an unstitched muslin buff charged with matchless white. I give it two alternating passes per side, and draw it down the wood again. I then check that it will slice paper cleanly. If the slice feels OK, I give it a few strops on a charged leather board and call it done. Occasionally, I go back to the belt for a quick touch-up, and repeat the rest of the process. I find this method quickly forms a good sharp edge that last a long time in normal kitchen use.
 
I recently discovered the joy of using diamond emulsion on my strop and it has fundamentally improved my work.
that said, a knife's edge is really the only wear component. Although I want my knives to leave my shop in as sharp a state as I can get them, it's also true that they are bound to lose that edge once they start getting used.
now that I'm taking on sharpening jobs, I realize how much edge deterioration most people seem comfortable with and use that knowledge to really perfect my edge geometries for a given use, and in some cases, a given user.
 
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I use diamond paddle strops (diamond paste on leather) to do the final sharpening/burr removal after a 325, then 1200 diamond stone. Usually do 14 micron diamond and then 3 micron diamond, but have been playing with a 40 micron diamond and 1 micron diamond, both on rough side leather lately and that seems to work pretty well!

I originally did 14 and 3 because that was roughly the same as my Bester 1200/Rika 5K water stone combo that I used on kitchen knives that left a great, aggressive edge. I wanted the strop to be able to actually sharpen and remove micro chips, not just strop at a super fine grit!
 
DevinT said:
There has been some discussion about sharpness and knives. The topic of burrs also came up.

A macro burr is also called a wire edge. It’s big enough to see and feel, they usually develop after doing the initial sharpening on a belt or a wheel.

A micro burr cannot usually be seen or felt. They are even difficult to see under magnification.

A macro burr runs the entire length of the sharpened edge. A micro burr can be sporadic and intermittent. (across the entire edge)

The finer the sharpening stone the finer the micro burr. This is why it doesn’t feel like there’s a burr when sharpening by hand.

Wayne Goddard recommends increasing the angle of the blade on the finishing stone and lightly drawing it to remove any burr and then do a few regular strokes to get it’s final sharpening.

I’ve seen guys use hard felt, pink eraser, hard wood etc. to pull the burr off. And then go back to the stone for a light resharpen. Not my favorite but works.

I like a loaded paddle strop for most knives and a hanging strop for straight razors.

Most of what I’ve learned about burrs is from using a straight razor and looking at the edge under magnification. A razor with a burr will tug on the whiskers.

Most knives feel sharp but still have a burr. Any burr will shorten the life of an edge.

Good luck out there

Much respect

Hoss
Click to expand...
Is the micro burr a separate burr or is it what’s left of the “root” of the macro burr once it has been removed? I’ve read some studies using SEM level magnification and it would seem that in some cases a significant amount of the root/base of the wire burr remains and becomes part of the apex. Given it is thick enough to be stable it doesn’t really present a problem. I’m curious if adjusting the angle on a stone is fully removing the burr or shaping whatever is left of the root to become a stable and useful part of the cutting edge. Perhaps it varies depending on the steel and sharpening angle?

There is a lot of interesting stuff going on at the apex of a knife edge. Unfortunately I don’t have a SEM setup to look at it.
 
For my customers I sharpen on a guided system for the sake of consistency. My deburring method is nano cloth loaded with 1 micron diamond at about .5 degree less or the same angle as my apex. Since the nano cloth compresses you can slightly convex an apex if you’re too aggressive. Then kangaroo strop loaded with .1 micron diamond at .1 degree greater than my apex. This should get rid of most of the root burr. However for the final blow I strop on a free hanging kangaroo strop with no compound. This further removes/reduces the burr. I’ve seen a drop of 40 Bess from the free hanging strop.
 
ScarFoot said:
Is the micro burr a separate burr or is it what’s left of the “root” of the macro burr once it has been removed? I’ve read some studies using SEM level magnification and it would seem that in some cases a significant amount of the root/base of the wire burr remains and becomes part of the apex. Given it is thick enough to be stable it doesn’t really present a problem. I’m curious if adjusting the angle on a stone is fully removing the burr or shaping whatever is left of the root to become a stable and useful part of the cutting edge. Perhaps it varies depending on the steel and sharpening angle?

There is a lot of interesting stuff going on at the apex of a knife edge. Unfortunately I don’t have a SEM setup to look at it.
Click to expand...
I certainly don’t have all the answers. I’m using a 500x power pocket microscope.

I was hoping this thread would bring more awareness and maybe more experience to the group.

I see lots of makers using poor sharpening techniques and no stropping or burr removal. Sharpening is a weak area for a lot of makers.

Hoss
 
DevinT said:
I certainly don’t have all the answers. I’m using a 500x power pocket microscope.

I was hoping this thread would bring more awareness and maybe more experience to the group.

I see lots of makers using poor sharpening techniques and no stropping or burr removal. Sharpening is a weak area for a lot of makers.

Hoss
Click to expand...
Understood. And I agree about sharpening being a weak area. It seems like it’s in an afterthought on a lot of knives I’ve handled at smaller shows. I’m constantly tinkering with my sharpening technique trying to make it better.

It’s never made sense to me that knives are generally stropped on flat, hard backed surfaces whereas straight razors generally use flexible hanging strops. From what I’ve read about straight razors (could be totally wrong) they’re generally designed to “self align” while stropping but it still seems like it would still roll the edge. Obviously it works anyway. I’ve never messed with straight razors though so I haven’t studied their edge geometry in depth. Maybe I’ll try making one sometime. That would probably help clear up a lot of the questions for me.
 
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