Deburring with a 3M Talc belt

[grepper]

Mr. Rupert most magnanimously sent me a 3M Talc belt to test to see how well it works for deburring.   Thank you Mr. Rupert!
 
My main interest in testing it was to discover if it might be a more efficacious solution than the leather belt I normally use.  The leather belt actually works very well for deburring, but it takes some practice and deburring must be done with care to remove burr on a toothy edge with a minimal amount of tooth smoothing.  I keep searching for something I can just jam a blade into, do a couple of swipes and automagically have a nice, burr free edge with little or no smoothing of the toothy edge. 
 
The surface of the talc belt is a fuzzy layer on a firm but slightly forgiving base.  Unfortunately this particular belt has a manufacturing defect where one of the two but joints was not properly glued and filled in so the belt is held together by only the tape on the back of the belt.  I was a little worried the thing might break, but because the Kally is a fairly slow 1x42 grinder generally the only damage done when a belt pops is that it is slightly startling.  Here you can see the fuzzy surface of the 3M talc belt and the thickness of the subsurface.
 
   
 
For consistency I used a 150 grit Cubitron belt for sharpening and raised a fine little burr visible to the unaided eye.
 
   
 
My normal procedure when using the leather belt is to first make 2 or 3 light passes at the angle of sharpening.  (1 pass = 1 swipe each side).  I do this to make sure the burr is straight and not mashed down on one side of the edge.  Then, holding the blade at almost 90° to the belt, very lightly swipe the length of the blade against the belt, doing this on both sides of the blade.  This forces an almost 90 ° bend in the burr which I hope aids in stress fracturing the burr.  Then I do a couple of passes at the angle of sharpening to bend the burr again, wipe it a few times on my jeans to clean the edge of dust and junk and I’m done.  This generally does a pretty good job of burr removal with a minimum amount of smooth of the edge.
 
So, I did the same thing with the talc belt.  Here is an image of the blade after the first couple of passes a sharpening angle.  You can see that the passes at sharpening angle do a good job of getting the burr to stand straight from the edge.

   
 
Then I completed the procedure with the 90° swipes, sharpening angle passes and jean wipes.  Here is the result.  Still lots of burr.
 
   
 
Bailing on the talc belt, I used the leather belt.  Here’s what it did.
 
   
 
A sharpness test on the PT50B after the leather belt yielded 145 gf.  About what I would expect.  Unless something has gone horribly amiss, this process almost always produces a 130 gf -150 gf edge.  I’ve done this so many times now, and it works so consistently, I can pretty much predict the sharpness reading, but I always take one anyway cuz I just like using the PT50B.
 
I suspect the talc belt is designed for polishing after loading it up with compound.  I really had my hopes, but for burr removal, at least in this one test, I found it less effective than a leather belt.  Alas, the search continues...

[Mark Reich]

I wouldn't worry about the splice. If you can find it useful, you can buy one with a regular diagonal splice. Mine runs true.

If you don't have a buffer, the talc belt will hold regular wax base buffing compound. I rub the bar on a stationary belt, on the platen, to load it well. I even try to rub it in with a nice, smooth, 1" steel pin, but a lot comes off.

I would rate it's abrasive ability between a sewn cotton and sisal wheel of a buffer. With the best emery compound it affects a stiff burr less than a leather belt, but it can remove soft burr pretty efficiently. A regular 2"x10" (or whatever) bar of buffing compound would last many years.

I can send a piece of emery if you want to pm your address.

[grepper]

Mr. Mark, Thank you kindly for you generous offer to send some emery, however for now at least I’m good to go on buffing and polishing supplies.
 
For me at least, burr removal is a real trip.  Even what appears to be a light burr has many of the same properties of a large gnarly burr.  Part of it is very easy to remove, but the part right next to the edge is more difficult.  It’s as though that last part next to the edge has become work hardened.  That’s just a guess on my part.  I suspect that Mr. Jan would be better able to explain what’s going on there that I can.
 
That last bit of burr can be difficult to impossible detect visually, even with a loupe.  It takes a microscope to really see it.  Interestingly, that last bit of burr can greatly affect sharpness to the tune of 200+ gf on the PT50B.  I’ve seen that many times.  I’ll sharpen a blade and check it for sharpness.  When I find it’s not as sharp as I expect, I’ll throw it under the microscope and, sure enough, there is still burr. 
 
Here is an example of what I’m talking about.  Check out the areas where the arrows point. 
 
   
 
That amount of burr is so small it requires a microscope to see it.  I can’t see it with my unaided eye or with a 10 X loupe, nor am I able to feel it with my fingers, yet it can greatly increase the sharpness reading.  However, even without a microscope when I get a sharpness reading that is not as sharp as expected, I always suspect remaining burr.  It’s actually highly indicative of same.
 
Of course when that happens it is pretty easy to test.  Just deburr more and if the sharpness drops into spec then that’s most likely what’s going on.  I’ve seen that so many times now that when I find myself in that situation I can guess with pretty high confidence burr is the culprit.
 
For me, the sharpening part is relatively easy.  Grind on one side and get as small a burr as possible.  Then do that on the other side.  As long as a constant sharpening angle was maintained during sharpening, chances are the blade is sharp.  Then the more difficult part, remove the burr without smoothing the nice toothy edge.
 
If the burr is not completely removed, the nice, sharp edge is not exposed and sharpness suffers.
 
Umm..., I’m no expert at this stuff, so please don’t take my word for it.  You know, try a bunch of stuff and see what pans out.  I’m just attempting as best I can to describe my own experience and how that experience impacts my thinking when I’m sharpening.

[Jan]

From general point of view there are two steel properties which directly influence the size of the burr:

1)     Steel ductility (brittle steels will not form large burrs),
2)     Strain-hardening coefficient (stainless steel, which work hardens easily, will form large burrs).

Jan