convex help

J

j_d

Joined
Jan 14, 2006
Messages
283
Gentlemen,
A while back I decided to switch from my edgepro (which I love) to convexing my large blade (busse shbm) with the mouse pad/sand paper and strop. I watched the knives ship free video and read what I could on here and launched into it.
I used to be able to get the standard v grind sharp enough to easily shave using the edge pro and strop. Using my convex method and stroping I can hardly get it to shave. I am convinced its sharp, I can push cut through the corner of a phone book with relative easy and the confetti flies as well and cleanly swiping through 1-1.5 inch grape vines in the woods with one pass. I dont consider it dull. In some ways it seems sharper than before but just wont shave worth a crap. Is this an issue of angle or am I missing something.
Thanks for any insight.
Josh
 
its possible that you're not removing the burr all the way or you are overstropping. try stropping the blade some more but watch the angle as you raise the spine up so you dont have it too high.
 
Sounds like you are using too much pressure or your backing might be too soft. Use less pressure in your finer grits and if your still not getting good results try a stiffer backing.
 
It can be very easy to put too much pressure (as has been said) with a bigger knife like that. Even letting the whole weight of a bm resting on the strop might be too much weight. keep it light.

also, to check my angle, I move the blade edge first on the strop (very very lightly and carefully). slowly increase the angle until the edge first tries to "bite" the leather, and that is your angle for stropping.

When I first started stropping I was having the exact same problem as you are describing. I could not get them hair jumping sharp. It seems like after a lighter touch and checking my angle's I got the feel for it.
 
I have recently been using a 1"x30" belt sander to produce great convex edges, basically a faster way than the mouse matt/sandpaper approach, but produces similar results.

What I have noticed is that if I do not create a burr initially on the coursest grit, I do not get that hair popping level of sharpness at the end of the process. As I progress to the finer grits, the burr gets finer each step. By the time I get down to the leather belt for the final finish, any remaining burr is removed and a hair popping shaving sharp edge is produced.

Maybe, if you are not yet doing so, try to create a burr on your initial course grit first, a burr that rolls from one side to the other as you swap sides, before going to the next finer grit sandpaper.
 
I just bought the 1x30 belt sander last week but I need to get some good belts for it. Which ones do you use and where did you get them?
 
I don't think recommending belt sanders to newbies is a good idea.

Unless you know what you're doing, power tools are like tequila- they just help you get into bigger trouble, FASTER.

If your angle is too great, the backing is too soft, or you press too hard it's easy to get the abrasive to come up too far and round off your edge. I've done that once or twice while stropping. Any of those things to a lesser extent (angle, backing, pressure) and you could find yourself with an edge that's much more obtuse than you thought- so it'll cut but won't shave.

Pick out an old knife you don't care about too much, ideally one that isn't already convexed, and practice putting a convex edge on it. I've been working on doing that with one of my paring knives the past few days, and I've learned a bunch. Nothing like hand's on.
 
GregY said:
I don't think recommending belt sanders to newbies is a good idea.
Click to expand...

I beleive that the first lesson in sharpening is to learn freehand on a stone. This teaches consistency in angle and handling skills. If you can sharpen freehand, you can always find something to sharpen your knife, in any situation you might find yourself in.

Saying that, knowing how to use a belt sander to produce convex edges is an extremely quick and easy way of getting great results. If you practice on old kitchen knives and other knives that have little value ( neighbours and mother in laws knives ) - then you have nothing to loose.

From reading the tutorial on the above link, I was able to produce a hair splitting edge on my first attempt - but I have been freehand sharpening knives for over 30 years.

I still like to pull out my Arkansas stones and produce an edge, its a great way to kill some time.
 
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