This convex edge is driving me crazy!

jesse2205

jesse2205

Joined
May 30, 2009
Messages
396
So I got this busse combat blade. It is a skinny ash1. The edge is so dull it wont cut one pice of hair off my arm no matter how hard I push down on my arm. As of now it barely cuts paper. I have been using the mousepad technique with 400 grit, 800 grit, 1000 grit, and then 1200 grit. After several hours of carfully sharpening the knife on the mousepad, using hardly any pressure at all pressing down on the knife, and using good technique, the blade is exactly the same sharpness as the way it was when i first got it. I have paper wheels, which I use the non gritted wheel to strop at the end, but it litterally does no good. The edge looks pretty desent. its nice and polished. I am at a loss to what is going on. I have looked at pretty much every youtube video, searched thoughout the entire forum looking for something I may have done wrong. I have tried pretty much everything there is to do. I even put sharpie marks along the edge to make sure I was hitting the right spots, and I was. Does anyone else have this problem? What should be my next step? Thanks.
 
Another question...If I go to harbor freight and buy a 1x30 belt grinder, will that work on putting a good convex edge on my knife? The highest grit they have is 120, so if I use that to put a good edge on the knife, then use the paper wheels to sharpen, would that work well?
 
Try a little bit less pressure, drop down to the 400 again, and lower the spine a tad. I'd bet that you've got a tad too much pressure, and it's rolling the paper up onto the cutting edge instead of just abrading the side.

I'd grab your belt from Harbor freight if you want to get an inexpensive one, then go to EconAbrasives and order a couple of belts in 180, 320 and 400, then one in 15 micron, and a leather stropping belt. Also a pound bar of the "Ultra Fine" green buffing compound. You'll end up into your system about $100, all told, and you'll be able to put a razor convex on a SHOVEL if you want to.

Before you go after that Busse, though, grab a couple of garage-sale cheepos to practice on. That belt takes metal off FAST! Couple of knives worth of practice to get the feel for it, though, and it works like a charm. I use a Kalamazoo belt grinder myself, and I can't recommend it highly enough. If you live up in the Pacific Northwest, you're more than welcome to drop past! Bring a couple knives, and I'll show you how to do it. It's not nearly as tough as it sounds. Took me longer to type out this post than it'd take to put an edge back onto your blade. :)

EDIT: Also, when you're sharpening with the belt, remember that heat is your enemy! Use light pressure, and after every couple of passes dip the blade in water to draw off any heat buildup before it starts. If the edge feels hot to your fingers as soon as it comes off the belt, you're getting a tad too much heat built up and you need to dip more frequently.
 
Komitadjie, do you use pressure on the blade when using the belt grinder or do you use a light touch like the mousepad, just enough to move the belt a tiny bit?
 
Depends on exactly what I'm trying to accomplish, but usually very, very little pressure. Just about enough that I can feel the blade touching the belt is all that's required. The common edge I produce, (working in the slack about a half-inch above the platen) is only lightly convex, although against a straight edge it clearly is. You get more convex the farther into the slack you go, with the most directly between the top wheel and the platen.

Get a cheap-o knife and play with it yourself a bit, it's a lot of fun seeing what it does as you move around and change technique. :)
 
If you aren't getting results with the sand paper I doubt the HF belt sander will be magic for you.

I use both the sandpaper/rubber base, and strop and have a HF as well.

With the HF I use the rougher belt to set the bevel on the thicker bigger knives. Then I finish it up on the sandpaper.

It can be very frustrating not getting results.

I had a convexed knife sent to me advertised as "scary sharp". It was dull enough that it would not slice paper, or scrape hair off the arm. It had a difficult time cutting plastic packaging even.

It took me a bit to figure the edge out.

If you cannot easily shave hair, and slice paper at the 400 grit level, you don't move on to a higher grit until you can.

It sounds like you are either not getting the very edge at all, or are "wrapping" the edge where the paper is coming back up the edge and actually dulling it.

Mousepads are a pretty soft backing, and some are much softer than others.

I now use a heavy dense rubber pad I got from Tandy Leather. It is much much more firm than my mousepad, and allows for more pressure without wrapping the edge. I still keep it light. With the mousepad, I don't even typically use the full weight of the knife!!!! (unless it is a small, light knife).

You might also be imparting a bit of wrist roll at the end of the stroke that can dull the edge.

I normally go down to 200 when doing any actual metal removal from the edge.

On some knives, heck I have used 60 to 80 grit at the initial setting of the bevel (don't recommend this to anyone with any worry about the satin finish, and not sure you need to go below 200 or 150).

I don't go any higher on the sand paper than 600 and then move on to a strop.

This yields hair popping edges.

You should be getting a wire edge at the 400 grit level before moving on. If you are not, you are not really getting the very edge.

The Harbor freight method will drastically increase the speed of setting the bevel, but you can really mess your edge up quick!!!!!!!

I will often hit the edge with the HF belt, (at a pretty low grit somewhere about 150 or so) and go straight to the strop and get scary sharp edges on some of my real beaters.
 
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Feel for a burr before moving to a finer grit. Use the coarsest grit first.

If you've raised a burr on both sides but your edge still isn't "sharp", another possibility is that you're either rounding off the edge or your edge bevel is too obtuse, and you should lower it down a bit.
 
Ok guys, since I last posted i've been busy, lol. Thanks for the comments. I went to harbor freight and got a $40 belt sander. I bought the highest grit belts they had (120 grit). I took it home, set it up, and took the 120 belts and rubbed them against each other to smooth em out a bit. I put the belts on the sander and got out a couple of cheap knives. First knife was a $20 gerber knife from walmart. I used light pressure being careful to maintain the correct angle and smoothly swiped it on the belt sander a few times. I could actually see the burr come up! First time in my life I could see a burr forming. Then, I took it to my paper wheels and stropped it, took the burr off and tested its sharpness. It sliced through arm hair like butter. It was crazy sharp! I then tried a few other knives, same result. Then, I felt confident to put my busse up to it. I ended up getting my busse really sharp. It mows through arm hair and slices through phone book paper with ease. I am satisfied now. My only problem I had was the edge on my knives. They were getting dull and rounded. So I went back over em and made sure I kept a constant angle throughout the edge. It helped enough to make the edges o.k. But I will take that considering I couldn't even cut paper a couple of hours ago. All my knives are sharper than they ever have been and I couldn't be happier. I find the belt sander/paper wheel combo to be the fastest, easiest way for me to get a crazy sharp edge. Its amazing what $40 at harbor freight will do for ya!!
 
I tried numerous methods and strops I made on my own, but much like you. The blades weren't getting sharp. I then purchased a JRE Industries Strop Bat and went through each compound with about 10 strokes on each side and it was sharp enough for me to accidently cut myself on.
 
Find yourself some finer belts, 120 will eat a lot of metal and take a lot of life from a blade. A 320 for setting bevels and a 600 for sharpening would make a big difference. Search for the thread on the HF 1x30, some excellent post from Jerry Hossom and lots of tips for use.
 
^ That.

My general-purpose belt is usually either a worn 180, or a fresh 320, followed by a 15 micron film belt, and leather. 120 is great for repairs and severely dull blades, but it'll remove a lot more metal than you actually need to. Jerry Hossom, Doug Rising, and "Twinblade" are all great sources of information, Doug was the one that started me out with the belt, and has provided an invaluable amount of information for keeping me on the straight-and-narrow. He was the one that advised me to start out with inexpensive belts and knives and work my way up, and is a very easy person to talk to. He really has his s**t together.
 
Micro-Surface sells 1"x30" Micro-Mesh belts as well. I only use my WorkSharp for belt sanding, which is only 1/2"x12", but I suspect I would prefer some nice cloth backed belts over the stiffer alternatives. Though where they really shine would be the finer grit belts like the 1200MX, which goes down to about 3 microns. Wouldn't be too hard to mirror polish steels like S90V with those.
 
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