Inconsistently Sharp

[zatch]

Hey guys, just some quick commentary on a change in my convex sharpening setup. If anyone else has had trouble using strops, this might help.

Over the past couple of years I have played around with different ways of sharpening and various sharpening systems. I started on a basic smith's kit with stones and rods and a few preset angles. I had an Edge pro system for a while (worked great). Now I'm pretty set on convex sharpening, whether it be sandpaper or on a system like the worksharp/belt sander.

Normally, I start with sandpaper on top of leather (wood as the base). Move up through grits, anywhere from 220 up to 2000, and finish on strops loaded with compound - black, green, then bare leather. I'm using the Bark River compounds and they work very well.

Here's where my commentary or perhaps a question comes in. While I get very sharp edges after finishing on bare leather, I've noticed that I get what I call "inconsistently sharp" results. Sometimes the edge is perfect; it really bites into fingernail/side of a pen, hair popping, etc...Sometimes it's still very sharp but doesn't have the same hair-popping, laser/screaming/bleeding/(insert favorite synonym) edge that I want. I've tried different angles, varying amounts of pressure, started with coarser grits, spent more time on higher grits, etc...It always ends up being inconsistently sharp. I have had my fair share of problems too (tips not being sharp, rounding out edges) but I have worked through those bad tendencies.

Everything I have read up until now, in terms of strops, is leather mounted on wood or something similar. A few weeks ago, after watching a youtube video, I spent some spare time converting all my strops to "free-hanging" strops. Same setup with the compounds, just without the backing...No more problems! I have used this "setup" around 15 times, all of which results in very consistent results, scary sharp edges.

Was my angle control that bad on wood-backed strops? I never had a problem with sandpaper on top of them. I have seen some really sharp edges come off wood back strops too.

Here's a couple of quick pictures to illustrate...

I use a couple of black paper clips to hold the leather in place. Eventually, I'll probably add a larger clip on the end of the leather. It's pretty compact. I have found that it doesn't take much work on each piece. 5 or 6 strokes per side, on each piece, and I'm golden. I made a mini version of this to take as a travel or portable kit.

Not the greatest example but at least a little proof. I couldn't be happier with the edges - very on par with a couple of extra sharp Bark Rivers I have. Also, this is all based on edges that were convex to begin with, or convex by the time they hit the strops.

Anyways, aside from the rambling, has anyone else received better results from free hanging strops (with or without compound)? My guess is I had bad angle control on the strops that was fixed by the free hanging leather. Either way, I'm much happier with this setup.

Comments, suggestions, criticisms are appreciated! :thumbup:

 

[zatch]

Few things to add - I plan on getting some newer, bigger pieces of leather (veg. tan from Tandy). The ones in the picture are old and need to be cleaned up. I eventually plan on using the smooth side rather than the rough as seen in the pic - at least for the bare leather piece.

The real question for me was, does it really matter? My edges were already 'sharp enough' for my tasks. Does having a slightly sharper edge make a difference? In my experience, it depends. I didn't notice the edge lasting any longer (or shorter). When slicing thinner materials, like paper or thin canvas, I noticed it was a little smoother/less resistance. I didn't notice a difference on cardboard boxes or on some cuts through paracord. I did notice a difference on wood though. It was able to get some pretty thin shavings off a block of wood I had laying around (much easier than I had before). Arguably, the difference could be inconsequential or minute for some...however, there is enough of a difference, for me at least, to make it 'worth it'...

All of this is based on my personal experiences and is quite obviously, not very scientific. YMMV....

 

[richard j]

i never use strops anymore since getting the paper wheels since the slotted wheel is a strop. i think its a lot easier to overstrop an edge on a flat strop laying on a table. i would say your free hanging strop would lessen the chance of overstropping the edge.

if you go too fine an edge it can roll on you. i never go over 400 grit before going to the slotted paper wheel to remove the burr. there have been a few members try coarser grit edges and they have found the edges last a lot longer than one taken down to say a half micron.

the knives i make are chisel grinds and i put a half convex edge on them with no more than a 400 grit edge before going to the slotted paper wheel and they hold up great. i have even went as low as 80 grit and had the knife treetop hairs.

 

[Obsessed with Edges]

I think most of the issue is more related to pressure on the hard-backed strop. Obviously, angle control is critical, but it's very easy to round off or roll the edge on a firmly backed leather strop, if pressure is just a little heavy. I've gravitated to stropping on wood, for the most part, because it can't deform/roll around the edge like leather can, assuming good angle control. When I do use leather, it's only after I've used the wood, and I approach it as if I were just wiping some dust off the edge, using very, very light pressure. Shouldn't see or feel the leather compress at all, if done correctly.

The hanging strop makes it difficult to compress the leather, which would otherwise curve/roll over the edge of the blade under heavy pressure. I think that's why you're seeing improvement, because your pressure is being somewhat automatically regulated.

Whether the enhanced sharpness matters or not, is entirely subjective to you and the needs/uses of your blades. There's a misconception that a 'refined' (polished) edge is inherently thin, and therefore weak. That's a too-thin edge or a wire edge, not necessarily a polished or 'refined' one. You can refine & polish a 40 degree inclusive edge, and it's no more likely to roll or fail than the same edge angle at a coarser grit. So long as the apex is pure and free of wires & burrs, a highly refined edge can make a significant difference in cutting (like you found with cutting wood), again depending on how you're using it. I've noticed great advantages to polishing convex edges, especially in cutting tough material like heavy cardboard. The round & smooth shoulders of the convex decrease resistance through the material, and then polishing those shoulders takes cutting resistance down even more. Slick-as-glass cutting through cardboard. And again, it still depends on the apex being as pure as you can make it.

 

[zatch]

if you go too fine an edge it can roll on you. i never go over 400 grit before going to the slotted paper wheel to remove the burr. there have been a few members try coarser grit edges and they have found the edges last a lot longer than one taken down to say a half micron.

I remember reading about this a while back (I can't recall where) and have always wanted to try it. The next time I start with lower grit sandpaper, I'm going to try finishing lower and see what happens. Personally, I'm starting to like strops just because of portability. It's nice to have a mini kit with me when I take longer weekend trips up north or something similar. Since I'm situated in an apartment (still in school ) a larger belt sander or paper wheels system is out of the question. It is one of the things I have always wanted to have.

 

[zatch]

I think most of the issue is more related to pressure on the hard-backed strop. Obviously, angle control is critical, but it's very easy to round off or roll the edge on a firmly backed leather strop, if pressure is just a little heavy. I've gravitated to stropping on wood, for the most part, because it can't deform/roll around the edge like leather can, assuming good angle control. When I do use leather, it's only after I've used the wood, and I approach it as if I were just wiping some dust off the edge, using very, very light pressure. Shouldn't see or feel the leather compress at all, if done correctly.

The hanging strop makes it difficult to compress the leather, which would otherwise curve/roll over the edge of the blade under heavy pressure. I think that's why you're seeing improvement, because your pressure is being somewhat automatically regulated.

Ah, that makes sense too. I have always tried to be critical of angle control. Same with pressure, but I never really thought it out; pressure (with leather) can round out or deform an edge just like bad angle control...I'll have to try using wood as a base rather than leather; it might prove that the problem I was having is due to pressure. I remember starting with a mousepad and sandpaper - I never had good results which would lead to frustration and putting more pressure into the pad :grumpy:

I through that last paragraph in just because it is exactly what I asked my self when I finally got the edge I was looking for. I can be too quick to judge or criticize without going out, using it, and drawing conclusions from using it in an everyday setting.

Whether the enhanced sharpness matters or not, is entirely subjective to you and the needs/uses of your blades. There's a misconception that a 'refined' (polished) edge is inherently thin, and therefore weak. That's a too-thin edge or a wire edge, not necessarily a polished or 'refined' one. You can refine & polish a 40 degree inclusive edge, and it's no more likely to roll or fail than the same edge angle at a coarser grit. So long as the apex is pure and free of wires & burrs, a highly refined edge can make a significant difference in cutting (like you found with cutting wood), again depending on how you're using it. I've noticed great advantages to polishing convex edges, especially in cutting tough material like heavy cardboard. The round & smooth shoulders of the convex decrease resistance through the material, and then polishing those shoulders takes cutting resistance down even more. Slick-as-glass cutting through cardboard. And again, it still depends on the apex being as pure as you can make it.

I completely understand what your saying and agree. I have not found an instance (yet) where a polished convex edge has hindered me from doing something. I have noticed that a knife with a fully convexed grind get's a bit sharper than just the edge being convex. I think this is mostly due to the edge being a bit thinner on the fully convex knives I have owned.

This is why I want to try the coarser edge idea and see if I can benefit from it. I'm still skeptical of it being able to hold an edge longer - I would think that has more to do with angle rather than grit, but I'm curious. I am always interested in trying new ways of doing things; I have always treated knife sharpening as a constant experimentation/learning experience.