The quest for a sharp edge(Sequel to What causes an edge to roll?) New photos 3/26/14

Squashfan said:
Heavyhanded, you and all the other master sharpeners are more than welcome to put in your 2 cents anytime. (In my case, you guys have put in 20 or 30 dollars worth!) I worry that some day you might get tired of trying to help me. I am a better sharpener from this thread. I redid the blackberry machete. I checked for a burr as I worked and raised only a small one. The edge preformed beautifully no damage as long as I limited myself to vines. Did not do well with half inch thick woody stems though. And it was raining a little bit when I was working. I kinda forgot to wipe the machete down so now I have some nice rust on the bevels. Whoops...

Forgot that I also changed my rake path. It did seem to help.
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Am not comfortable with the master title, but definitely have plenty of opinion I'm willing to share, and am happy its helping. It's very difficult to convey a lot of these concepts in print - many don't even come across well in video.

I have experimented quite a bit with rake angles and am convinced that overall a 45* path is best for angle stability. As you begin to go more perpendicular or more parallel, it feels less stable, more prone to small wobble - might be just me...

For the machete, the paper over stone with compound is your best friend. Use two or three sheets of paper and your finest compound assuming it isn't damaged - if it is, start with the black compound and clean it up first. Use some pressure, more than you'd use on a fixed abrasive - don't be concerned with a bit of microconvexing at the edge, is a good trade-off for toughening up the apex and reducing friction going into the chop. This type of tool needn't be three finger sticky though it should shave arm hair.

The 7th video in the Washboard series shows a field method for touching up a machete - in fact the one I use for the demo was left hanging in a tree for two weeks in a canvas sheath and needed to be cleaned up just to remove the rust blossoms. Can also do this sort of tool on a bench stone working in overlapping sections, or use the method I demonstrate by wrapping sandpaper around the stone and using exactly as shown. You could use the bench stone as is, but then have issues of keeping oil on it, or using it dry and maybe plugging or glazing it, so in this instance the SiC sandpaper is ideal.

On a side note, by the end of the video you can see how much swarf is building up on the knee of my jeans, and why I always emphasize taking care of whatever you're using to grind/taking into account that removed steel and any stone debris that might form - left to its own, it will negatively effect grinding quality and in many cases actually cause harm to the abrasive surface.

Martin
 
HeavyHanded said:
The 7th video in the Washboard series shows a field method for touching up a machete - in fact the one I use for the demo was left hanging in a tree for two weeks in a canvas sheath and needed to be cleaned up just to remove the rust blossoms.

Martin
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Correction - is the 6th video. Not sure why exactly but was one of my favorites to do.
 
I stopped with black compound over stone and it was pleennttyy sharp. I had two black berry vines and some kind woody stem bunched really close together. The vines were at least a good quarter inch thick in diamater and the stem was larger than that. I was planning to get each stalk individually but the machete went through all three in one go! :eek::eek::eek: I didn't even mean to do that and it was just a standard pinch grip swing!
 
Squashfan said:
I stopped with black compound over stone and it was pleennttyy sharp. I had two black berry vines and some kind woody stem bunched really close together. The vines were at least a good quarter inch thick in diamater and the stem was larger than that. I was planning to get each stalk individually but the machete went through all three in one go! :eek::eek::eek: I didn't even mean to do that and it was just a standard pinch grip swing!
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Nice work! Plan your cuts carefully...
 
I ought to go back and get a picture of the stems since I will cut them off at the ground later. And, yes, I will have to be more careful, lol. The machete really did surprise me with it's performance. I sharpened it with the one of the stones that came with my Marble's machetes. They are very coarse already and I lapped this one, which makes the grit even coarser. So it must be a really, really toothy edge.
 
Squashfan said:
I ought to go back and get a picture of the stems since I will cut them off at the ground later. And, yes, I will have to be more careful, lol. The machete really did surprise me with it's performance. I sharpened it with the one of the stones that came with my Marble's machetes. They are very coarse already and I lapped this one, which makes the grit even coarser. So it must be a really, really toothy edge.
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Using the compound over a stone can profoundly effect the edge even following a relatively coarse stone, and IMHO makes for the perfect hard chopping finish - very low friction with a lot of edge uniformity. Is also very fast to whip up and maintain. Lacks some of the bite I prefer in my smaller EDU knives, but anything that isn't expected to draw-cut doesn't need tooth anyway.

I found some old pics I took of a progression. First pic is straight off a Norton India stone, steel is Aus8. Second pic is after stropping with light pressure on some white compound (or maybe Flexcut Gold, I cannot remember) on paper wrapped around the fine side of the India stone - is a bit more refined but still plenty of variation in line and depth. Third pic is the same edge after being stropped on paper over the coarse side of the India stone with a bit more pressure - just enough to feel the stone texture and maybe 15-20 passes/side.

The change is tremendous. Note, this edge lost a lot of bite and you can tell by the bit of blurring along the apex that it did microconvex a little, still only a degree or two but enough to effect performance. This edge still could shave arm hair cleanly and IIRC was able to whittle a hair after being heavily stropped on plain paper for 50-60 passes after this image was taken. Is not a very "technical" edge, but for those who don't believe its worth the time to polish machetes and hatchets, this method works so fast and easy there's no reason not to. The difference in performance is well worth the minimal time and effort. A similar effect can be had by using three or four sheets of compressed paper on a Washboard to eliminate some of the microtooth it imparts.


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Sigh, you can produce an edge that blows anything I can do out of the water. Tried changing my rake angle on the Klein knife and it did help. Still to much burr though, so it was flip, flip, flip, flip with compound. I cut the apex off on my fine stone. I will try again tomorrow.
 
Cutting the apex off because you have a burr will not change anything. The burr is a constantly changing object as it's being ground and it's always "new" never flipped. It does seem as it flips but when you run the abrasive over the edge your are always removing steel and replacing old burrs with new ones.

You will notice that the density of the abrasive media and the pressure you apply play a HUGE role in the size of the burr formation. For example; a spyderco ceramic with its high density can roll a edge just from the pressure of the edge sitting on the stone and when sharpening you can easily produce wire edges with the lightest of touch. A leather strop coated with compound on the other hand is too soft to produce the same level of deflection and deformation which reduces burr formation to a near non-existent point.
 
Thank you for your advice. I cut the apex off as a hard reset because I could not fix the edge. Then let me rephrase what I said. Nothing I tried would remove the burr WITHOUT generating a new burr. I tried my leather strop but I don't have the angle and pressure control down yet. Is all I need to do reduce pressure on the stone?
 
Squashfan said:
Thank you for your advice. I cut the apex off as a hard reset because I could not fix the edge. Then let me rephrase what I said. Nothing I tried would remove the burr WITHOUT generating a new burr. I tried my leather strop but I don't have the angle and pressure control down yet. Is all I need to do reduce pressure on the stone?
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If your burr appears to be flipping its because that's exactly what's happening. It may be adding some reinforcements, but the bulk of the original is almost certainly still there. The burr is unsupported steel - it falls outside the lines formed by the bevel angles. It needs to be abraded away or torn off. To abrade it away you need to use less pressure than it takes to collapse it back to the opposite side of the angle, but enough pressure that whatever abrasive you're using can still grind it off. Less pressure at every stage will help considerably, as will not allowing it to flip too many times in the first place. A strop can generally only remove fairly small burrs and unless very firm, will almost always come at some expense in edge geometry.

Final removal on a stone will likewise be helped greatly by seriously reducing pressure - just enough for the abrasive to work it off. Elevating the spine can help as well but is problematic in that it can create another bevel transition (microbevel) if you don't stop at the right point. This works by coming at it from a more advantageous angle - is less likely to collapse under pressure when approached at a steeper angle. As the angle you approach the burr from becomes more shallow, the less pressure it can tolerate before turning up. Use shorter strokes and less pressure and observe every pass or two. The burr is made of steel just like the rest of the edge, is just much weaker. Grind it off just like the rest of the edge but with less pressure and stop when its gone. If you keep going, you'll grind across the existing apex and start to form a burr on the opposite side. The key to burr removal in this manner is to stop at the right time - observe often.

If removing a small one while backhoning on a hard strop, lapping board, or waterstone, you can also drag the edge across some wood with every pass or so, backhone, drag, backhone etc and the burr will disintegrate under the alternating pressures. This is (IMHO) not as reliable as grinding it off with intent, but works surprisingly well - use light pressure. Murray Carter uses this method in some of his videos - very sparingly toward the end of a sharpening job. I tend to use it a bit more "aggressively" while I'm still working the edge - still light pressure but I start sooner and use it every time for a number of backhone passes, then once I'm certain the burr is gone I'll finish with a couple very light and no drag across the wood.


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I had gotten the burr to the stage when the pressure to flip was less than the pressure to remove. I hate that stage because I have stuck there for the past 8 or 9 months. But I have had some experience with a burr just falling off with compound and I like that feeling. I think I will have to take a break on sharpening for a little bit. I will still be on here and posting. However, I am starting to feel burnt out and I can't do my best work like that. But when I pick it back up, I will be better than before because I am getting a good idea of what I need to do. And how to do it.

One thing did happen last night. I was sitting at the stone sharpening when all of a sudden I felt the feedback increase. It was accompanied by a change in the sound of the blade on the stone. First time that I had noticed that.
 
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