I did a write up for another member here on sharpening convex edges using sandpaper and a soft backing. Hopefully, he will chime in soon and share his progress so far after he followed my amateur advice in sharpening his BK9 and 2.
I can get my blades razor sharp doing this, but it is all sharpening preference and it takes practice.
Here ya go!
So I am going to hit bare basics on grits/equipment, techniques, pressure and things to try in this e-mail just to make an attempt to cover as many bases as I can so I apologize if I am feeding you crap you already know. So, with that said, here we go!!!!
To start off, convex sharpening is way different than the more or less 'traditional' v-edge sharpening we see everyday on the forums. Some people use stones, some people use sandpaper and others are lucky enough to have a belt sander. I, myself, am a member of the sandpaper crowd since it is inexpensive, plentiful, very versatile piece of equipment IMO.
In this method of convex sharpening, the knife is 'stropped' spine-first, staring either at the edge closest to the handle or at at the far end of the blade. When stropping, moderate pressure is used as you make each pass and follow the belly in a smooth motion. It is possible to convex on stones as well; there are many methods. You can go in circles on the stone, push the blade back and forth...basically any motion where there is a slight and constant variation of the angle will create the convex edge.
To really get you going, there is a series of videos here that explain the basics of convex sharpening. THESE WILL HELP YOU A TON!!!!!!!!!!!!!!!
Equipment:
When I began to sharpen convex edges, I used the mouse-pad method like many others do on the forums. For some reason, I could never get the hair-popping edge no matter what I did. In a fit of inspiration, I went to home depot and picked up one of those Norton sheet sanders (the one I posted in the forums) to put in my field kit. I really liked it since the paper clipped in and is held securely in place; no need to hold it with one hand like I did with the mouse-pad. The foam pad it has also was a bit stiffer than the pad I was using. This combo is what seemed to really get my working edges to evolve into 'scary as hell sharp' very quickly.
This is my current set up now
-Norton sheet sander
-220, 400, 600, 1000, 2000 grit sand paper
-strop w/ green compound (I hear that Bark River white is incredibly great too; I have both green and black, but I never use the black.)
If you end up using a mouse-pad, I would try to find a way to secure the paper firmly so it does not slide by accident...I cannot tell you how many dang edges I have rolled from the paper slipping on me!!!
You can use many things. I know people who use the belts from belt sanders, put one end on a tree branch and the other in their hand and sharpen that way! People put their paper on their leather strops instead of mouse-pads too...as long as it is a soft backing like that, it will work 9 times out of 10.
Grits/when to change grits/ pressure/angles/tips...SHARPENING with a soft backing!
****So, before we start let me run down grits I use really quickly.
-100: I use this for re-profiling a really damaged blade. It takes off a lot of metal and I really do not think you need to go any lower than this. I usually start with 100 when I am taking off a factory edge. I did this with my BK2 to knock off the shoulders and thin her out a bit; it is not a full-height convex, but it is close! Do not use it every time you need to sharpen due to how coarse it is...but you probably know that already!
-220: I use it for re-profiling as well, but really only for minor kinks in the edge. I took my 14 to it today since the edge hit an eyelet in its kydex sheath and f*cked it up, and after about 2 or 3 minutes, it was good as new.
-400: I usually start here for general sharpening if I have a working edge on it. You know, the 'it is sharp enough to do what I need it to, but it won't slice paper very well' kind of sharp.
-600: More or less equivalent to a fine sharpening stone. You do not really have to go past this since anything over 600 is polishing the edge, but we are knife nuts!!! I mean, for the average person, that is adequate...but if you want scary sharp demon edges, you need to get that edge as fine and polished as possible.
-1000: 1st polishing, working out scratches from 600 grit..
-2000: making those micro serrations and burrs as small as possible before hitting the strop, working out scratches from 1000 (should be mirror polished or near mirror by now)
-Strop w/ compound: removes final burr, polishes edge. I strop my blades constantly as I use them. If you keep them honed, you do not need to keep sharpening all of the time, so strop when you can. I bring a small strop in the field with me (piece of leather with compound) for this.
****Moving up grits and the like
So, you are sharpening your BK2, right? Well, to start, how is the edge right now? Is it duller than a bookworm's social life? Does it still have a factory edge? Based on what it is right now, you must choose the appropriate grit. I would start at 220 or possibly 100 to make it go a little faster. You remember the technique on the video right? 3 motions: back, turn, down...right?
Let's say you go with 100 grit. Start with whichever method you are most comfortable with (I go from tip to heel) using moderate pressure. If you use too much pressure, the paper will actually come up and blunt the edge!! If you go from tip to hell like me, begin to strop spine first and drop you hand straight down to hit that edge on the belly perfectly. I am serious, practice that really quickly (even if you do it on the tabletop). To hit the belly without messing up, you must drop your hand downwards slightly as you are doing the stropping motion just enough for the edge to be sitting on the paper. (I can add my own pics and the ones Richard sent me if you need more visuals)
If you are going from heel to tip (like in the video), raise your hand up to match the edge. You will get the motion down after some practice. After a while, it becomes second nature. This motion is in Sharpening video 4 on that website.
Since you are just beginning, I would recommend that you do a pass on one side of the blade, flip it over, and do a pass on the other side to ensure everything is even. A good method to see where exactly you are hitting is to use a sharpie and mark the edge/ area that you want to hit. This give you a visual conformation that your technique is correct or needs some adjustment. The edge should be 'sitting on the paper'. Not digging in, not hovering slightly above....it should be right on there like in the videos.
Sharpen until the edge is the shoulders are knocked off and it has that nice convex shape, has a heightened level of sharpness (mine usually won't shave but it will slice paper fairly well) and that the scratch pattern is done changing. Once you get to that point where the level of sharpness and scratch pattern stays the same, STOP! From there, it is time to move up. Switch out whatever grit you were using and put up the next successive (Ex: 100 to 220, 200 to 400, 400- 600, etc). Do the same thing as last time but with slightly less pressure than last time. Do this until the level of sharpness and scratch pattern do not change and stop. It is important to note that as you move up the grits, ease up on the pressure a little each time. By the time you are up to 2000, it should be almost no pressure at all. After each grit, the level of sharpness should also be getting better as well; getting sharper and sharper as you get finer and finer.
Tips:
-Remember to ease up on pressure as you get higher in the grits
-Use a sharpie to mark the edge for visual conformation on technique and angles
-Haste makes waste
-Raise/lower your hand to follow the curve of the belly
-always check the scratch patterns/sharpness level after a while to see if they are still changing on each grit
-re-profiling takes time so be patient!
-make sure the paper is as secure as you can get it on your padded surface to minimize messing up your edge
-as you get better, you can actually 'feel' what is going on better as you are stropping
-do not skip grits to ensure the most polished edge
-putting a padded surface on a wooden pole with sandpaper can convex sharpen recurve blades
Once you have gone up all the way to 2000 (1000 is fine, but some people go all the way up to 8000 and crazy sh*t like that too...whatever works for you!!), it is time to finish up that edge with a strop. A strop is that line that separates an ok edge to a crazy sharp edge. Using the exact same method on the sandpaper, strop your blade along it. I use enough pressure to where the edge 'sticks' to the strop. It is something you have to feel for. When I strop after use, it tends to 'stick' more; after sharpening, it tends to glide more than 'stick' so do not fret if it isn't sticking after sharpening!!!!!!
Testing Sharpness
There are many ways to test sharpness, but many have too many variables in them. Slicing paper is a good test, but since there are so many different kinds, it is difficult to have consistent results. Cigarette papers are great for when you have a REALLY fine edge to test. Printer paper or notebook paper is good too ince the easier it slices through thinner paper, the sharper it is (more or less). Shaving arm hair can be very iffy because everybody is different!! Well, you also have bald spots too but...yeah..My arm hair is very fine. this means that if my edge is really good, it will pop right off. My leg hair, on the other hand, is coarser and is easily shaved on edges that could not pop off my arm hair. Basically, measuring sharpness is very complex; do what you see as best fit. My favorite test: USE IT FOR WHAT YOU WOULD USE THAT BLADE FOR! Seriously, it is the best test of all IMO.
There are also systems like the Lansky, work-sharp, etc. that could help ya.
Also, go easy ripping apart my advice, I'm still learning too
-Good luck and take care buddy.
-Deadfall
